PHP: Difference between revisions
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{{Infobox programming language |
{{Infobox programming language |
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| logo = [[File:PHP |
| logo = [[File:PHP-logo.svg|frameless]] |
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| caption = PHP: Hypertext Preprocessor |
| caption = PHP: Hypertext Preprocessor |
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| file ext = .php, .phtml, . |
| file ext = .php, .phtml, .php4, .php3, .php5, .phps |
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| paradigm = [[imperative programming| |
| paradigm = [[imperative programming|imperative]], [[functional programming|functional]], [[object-oriented programming|object-oriented]], [[procedural programming|procedural]], [[reflective programming|reflective]] |
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| released = {{start date and age|1995}}<ref name="mysqlconference">{{cite web | last=Lerdorf | first=Rasmus | title=PHP on Hormones – history of PHP presentation by Rasmus Lerdorf given at the MySQL Conference in Santa Clara, California | date=2007-04-26 | accessdate=2009-12-11 | publisher=The Conversations Network | url=http://itc.conversationsnetwork.org/shows/detail3298.html }}</ref> |
| released = {{start date and age|1995}}<ref name="mysqlconference">{{cite web | last=Lerdorf | first=Rasmus | title=PHP on Hormones – history of PHP presentation by Rasmus Lerdorf given at the MySQL Conference in Santa Clara, California | date=2007-04-26 | accessdate=2009-12-11 | publisher=The Conversations Network | url=http://itc.conversationsnetwork.org/shows/detail3298.html }}</ref> |
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| designer = [[Rasmus Lerdorf]] |
| designer = [[Rasmus Lerdorf]] |
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| developer = [[ |
| developer = [[The PHP Group]] |
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| latest release version = |
| latest release version = 5.5.15<ref>{{cite web |url=http://php.net/archive/2014.php#id2014-07-24-1 |title=PHP 5.5.15 is released |work=News Archive - 2014 |date=2014-07-24 |accessdate=2014-07-27 |publisher=php.net}}</ref> |
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| latest release date = {{start date and age| |
| latest release date = {{start date and age|2014|07|24}} |
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| latest preview version = 5.6.0RC3<ref>{{cite web |url=http://www.php.net/archive/2014.php#id2014-07-31 |title=PHP 5.6.0RC3 is available |work=News Archive - 2014 |date=2014-07-31 |accessdate=2014-08-01 |publisher=php.net}}</ref> |
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| latest preview date ={{start date and age| |
| latest preview date = {{start date and age|2014|07|31}} |
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| frequently updated = yes |
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| typing = [[dynamic typing|Dynamic]], [[weak typing|weak]] |
| typing = [[dynamic typing|Dynamic]], [[weak typing|weak]] |
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| implementations = [[Zend Engine]], [[HHVM]], [[Phalanger (compiler)|Phalanger]], [[Quercus (software)|Quercus]], [[Project Zero]], [[Parrot virtual machine|Parrot]] |
| implementations = [[Zend Engine]], [[HHVM]], [[Phalanger (compiler)|Phalanger]], [[Quercus (software)|Quercus]], [[Project Zero]], [[Parrot virtual machine|Parrot]] |
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| dialects = |
| dialects = |
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| influenced by = [[Perl]], [[C (programming language)|C]], [[C++]], [[Java (programming language)|Java]], [[Tcl]]<ref name="mysqlconference" /> |
| influenced by = [[Perl]], [[C (programming language)|C]], [[C++]], [[Java (programming language)|Java]], [[Tcl]]<ref name="mysqlconference" /> |
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| influenced |
| influenced = [[Hack (programming language)|Hack]] |
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| programming language = [[C (programming language)|C]] |
| programming language = [[C (programming language)|C]] |
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| operating system = [[ |
| operating system = [[Cross-platform]] |
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| license = [[PHP License]] (most of Zend engine under [[Zend Engine License]]) |
| license = [[PHP License]] (most of Zend engine under [[Zend Engine License]]) |
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| website = {{URL|//php.net}} |
| website = {{URL|http://php.net}} |
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| wikibooks = PHP Programming |
| wikibooks = PHP Programming |
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}} |
}} |
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'''PHP''' is a [[server-side scripting]] language designed for [[web development]] but also used as a [[general-purpose programming language]]. Originally created by [[Rasmus Lerdorf]] in 1994,<ref name="History of PHP">{{cite web|title=History of PHP|url=http://php.net/manual/en/history.php.php| |
'''PHP''' is a [[server-side scripting]] language designed for [[web development]] but also used as a [[general-purpose programming language]]. {{As of|2013|1}}, PHP was installed on more than 240 million [[website]]s (39% of those sampled) and 2.1 million [[web server]]s.<ref>{{cite web | url=http://news.netcraft.com/archives/2013/01/31/php-just-grows-grows.html | title=PHP just grows & grows | date=2013-01-31 | accessdate=2013-04-01 | author=Ide, Andy}}</ref> Originally created by [[Rasmus Lerdorf]] in 1994,<ref name="History of PHP">{{cite web|title=History of PHP|url=http://www.php.net/manual/en/history.php.php|publisher=php.net}}</ref> the [[reference implementation]] of PHP (powered by the [[Zend Engine]]) is now produced by The PHP Group.<ref name="about PHP">{{cite web|accessdate=2008-02-25|url=http://www.php.net/history|title=History of PHP and related projects |publisher=The PHP Group}}</ref> While PHP originally stood for ''Personal Home Page'',<ref name="History of PHP" /> it now stands for ''PHP: Hypertext Preprocessor'', which is a [[recursive acronym]].<ref>[http://www.php.net/manual/en/preface.php PHP Manual: Preface], www.php.net</ref> |
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PHP code |
PHP code can be simply mixed with [[HTML]] code, or it can be used in combination with various [[Web template system|templating engines]] and [[web framework]]s. PHP code is usually processed by a PHP [[interpreter (computing)|interpreter]], which is usually implemented as a web server's native [[plugin (computing)|module]] or a [[Common Gateway Interface]] (CGI) executable. After the PHP code is interpreted and executed, the web server sends resulting output to its client, usually in form of a part of the generated web page{{snd}} for example, PHP code can generate a web page's HTML code, an image, or some other data. PHP has also evolved to include a [[command-line interface]] (CLI) capability and can be used in [[Computer software|standalone]] [[graphical user interface|graphical applications]].<ref>{{cite web | url = http://www.php.net/manual/en/intro-whatcando.php | work = PHP Manual | title = Introduction: What can PHP do? | accessdate = 2009-03-05}}</ref> |
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The |
The canonical PHP interpreter, powered by the Zend Engine, is [[free software]] released under the [[PHP License]]. PHP has been widely ported and can be deployed on most web servers on almost every [[operating system]] and [[computing platform|platform]], free of charge.<ref name="foundations" /> |
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Despite its popularity, no written [[Formal specification|specification]] or standard exists for the PHP language; instead, the canonical PHP interpreter serves as a [[de facto]] standard. However, work on creating a formal specification has started in 2014.<ref>{{cite web|last1=Jackson|first1=Joab|title=PHP gets a formal specification, at last|url=http://www.itworld.com/software/429534/php-gets-formal-specification-last|website=ITworld|publisher=[[IDG]]|date=2014-07-31}}</ref> |
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== History == |
== History == |
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=== Early history === |
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|image1=Rasmus Lerdorf cropped.jpg |
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PHP development began in 1994 when [[Rasmus Lerdorf]] wrote |
PHP development began in 1994 when the developer [[Rasmus Lerdorf]] wrote a series of [[Common Gateway Interface]] (CGI) [[Perl]] scripts, which he used to maintain his [[personal homepage]]. The tools performed tasks such as displaying his résumé and recording his [[web traffic]].<ref name="about PHP"/><ref> |
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{{cite web | url = http://itc.conversationsnetwork.org/shows/detail3298.html | title = PHP on Hormones | format = mp3 | last = Lerdorf | first = Rasmus | publisher = The Conversations Network | date = 2007-04-26 | accessdate = 2009-06-22 }}</ref><ref>{{cite web | url = http://talks.php.net/show/mysql07key/3 | title = Slide 3 | work = slides for 'PHP on Hormones' talk | last = Lerdorf | first = Rasmus | publisher = The PHP Group | year = 2007 | accessdate = 2009-06-22}} |
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</ref> |
</ref> He rewrote these scripts in [[C (programming language)|C]] for performance reasons, extending them to add the ability to work with [[web form]]s and to communicate with [[database]]s, and called this implementation "Personal Home Page/Forms Interpreter" or PHP/FI. |
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PHP/FI could be used to build simple, dynamic [[web application]]s. |
PHP/FI could be used to build simple, dynamic [[web application]]s. Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" publicly to accelerate [[software bug|bug]] location and improve the code, on the [[Usenet]] discussion group ''comp.infosystems.www.authoring.cgi'' on June 8, 1995.<ref> |
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{{cite web|url= http://groups.google.com/group/comp.infosystems.www.authoring.cgi/msg/cc7d43454d64d133?pli=1 |title=Announce: Personal Home Page Tools (PHP Tools)|last=Lerdorf|first=Rasmus|date=June 8, 1995 |
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|accessdate=7 June 2011}}</ref><ref>{{cite newsgroup | title = Announce: Personal Home Page Tools (PHP Tools) | author = Lerdorf, Rasmus | date = 1995-06-08 | newsgroup = comp.infosystems.www.authoring.cgi | url = http://groups.google.com/group/comp.infosystems.www.authoring.cgi/msg/cc7d43454d64d133 | accessdate = 2006-09-17}}</ref> This release already had the basic functionality that PHP has {{as of | 2013 | lc = on}}. This included Perl-like variables, form handling, and the ability to embed HTML. The [[syntax]] resembled that of Perl but was simpler, more limited and less consistent.<ref name="about PHP"/> |
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Early PHP was not intended to be a new programming language, and grew organically, with Lerdorf noting in retrospect: "I don’t know how to stop it, there was never any intent to write a programming language […] I have absolutely no idea how to write a programming language, I just kept adding the next logical step on the way."<ref name=itconversations>{{cite web |
Early PHP was not intended to be a new programming language, and grew organically, with Lerdorf noting in retrospect: "I don’t know how to stop it, there was never any intent to write a programming language […] I have absolutely no idea how to write a programming language, I just kept adding the next logical step on the way."<ref name=itconversations>{{cite web |
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|date=2003-11-19 |
|date=2003-11-19 |
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|url=http://itc.conversationsnetwork.org/shows/detail58.html |
|url=http://itc.conversationsnetwork.org/shows/detail58.html |
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|archiveurl= |
|archiveurl=http://web.archive.org/web/20130728125152/http://itc.conversationsnetwork.org/shows/detail58.html |
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|archivedate=2013-07-28 |
|archivedate=2013-07-28 |
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}}, cited at {{cite web |title=This Is Not Another "PHP Sucks" Article |url=http://blog.feliperibeiro.com/this-is-not-another-php-sucks-article |
}}, cited at {{cite web |title=This Is Not Another "PHP Sucks" Article |url=http://blog.feliperibeiro.com/2012/08/this-is-not-another-php-sucks-article.html |author=Felipe Ribeiro |date=Aug 7, 2012}}</ref> A development team began to form and, after months of work and [[Beta development stage|beta]] testing, officially released PHP/FI 2 in November 1997. |
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{{Anchor|ORGANIC}} |
{{Anchor|ORGANIC}} |
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One criticism of PHP is that it was not originally designed, but instead it was developed organically;<ref name=itconversations /> among other things, this has led to inconsistent naming of functions and inconsistent ordering of their parameters.<ref>{{cite web|title=Problems with PHP|url=http://toykeeper.net/soapbox/php_problems/|accessdate=20 December 2010}}</ref> In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping",<ref>{{cite web|url=http://news.php.net/php.internals/70950 |title=php.internals: Re: Function name consistency |publisher=News.php.net |date=2013-12-28 |accessdate=2014-02-09}}</ref> while in some very early versions of PHP the length of the function names was used internally as a [[hash function]], so names were chosen to improve the distribution of hash values.<ref name="php-internals-70691">{{cite newsgroup |title=Re: Flexible function naming |author=[[Rasmus Lerdorf]] |date=Dec 16, 2013 |newsgroup=php.internals |url=http://news.php.net/php.internals/70691 |accessdate=December 26, 2013}}</ref> |
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[[Zeev Suraski]] and [[Andi Gutmans]] rewrote the [[parser]] in 1997 and formed the base of PHP 3, changing the language's name to the [[recursive acronym]] ''PHP: Hypertext Preprocessor''.<ref name="about PHP"/> Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new [[rewrite (programming)|rewrite]] of PHP's core, producing the [[Zend Engine]] in 1999.<ref>{{cite web | title = Zend Engine version 2.0: Feature Overview and Design | publisher = [[Zend]] Technologies Ltd. | url = http://www.zend.com/zend/zend-engine-summary.php | accessdate = 2006-09-17 }}</ref> They also founded [[Zend Technologies]] in [[Ramat Gan]], Israel.<ref name="about PHP"/> |
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=== PHP 3 and 4 === |
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[[Zeev Suraski]] and [[Andi Gutmans]] rewrote the [[parser]] in 1997 and formed the base of PHP 3, changing the language's name to the [[recursive acronym]] ''PHP: Hypertext Preprocessor''.<ref name="about PHP"/><ref>{{cite web|title=PHP - Acronym Meaning Vote|url=http://web.archive.org/web/20000815063125/http://il.php.net/vote_listing.php3|website=PHP.net|archivedate=15 August 2000}}</ref> Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new [[rewrite (programming)|rewrite]] of PHP's core, producing the [[Zend Engine]] in 1999.<ref>{{cite web | title = Zend Engine version 2.0: Feature Overview and Design | publisher = [[Zend]] Technologies Ltd. | url = http://www.zend.com/zend/zend-engine-summary.php | accessdate = 2006-09-17 }}</ref> They also founded [[Zend Technologies]] in [[Ramat Gan]], Israel.<ref name="about PHP"/> |
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On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released.<ref name="about PHP"/> As of August 2008 this branch reached version 4.4.9. PHP 4 is no longer under development nor will any security updates be released.<ref name="2007 news">{{cite web|title=php.net 2007 news archive|url=http://www.php.net/archive/2007.php|publisher=The PHP Group|accessdate=2008-02-22|date=2007-07-13}}</ref><ref>{{cite web|accessdate=2008-03-16|url=http://www.internetnews.com/dev-news/article.php/3725291|title=PHP 4 is Dead—Long Live PHP 5 |publisher=InternetNews|date=2008-02-01|author=Kerner, Sean Michael}}</ref> |
On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released.<ref name="about PHP"/> As of August 2008 this branch reached version 4.4.9. PHP 4 is no longer under development nor will any security updates be released.<ref name="2007 news">{{cite web|title=php.net 2007 news archive|url=http://www.php.net/archive/2007.php|publisher=The PHP Group|accessdate=2008-02-22|date=2007-07-13}}</ref><ref>{{cite web|accessdate=2008-03-16|url=http://www.internetnews.com/dev-news/article.php/3725291|title=PHP 4 is Dead—Long Live PHP 5 |publisher=InternetNews|date=2008-02-01|author=Kerner, Sean Michael}}</ref> |
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=== PHP 5 === |
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On July 13, 2004, PHP 5 was released, powered by the new Zend Engine II.<ref name="about PHP"/> PHP 5 included new features such as improved support for [[object-oriented programming]], the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements.<ref>{{cite web|title=Why PHP 5 Rocks!|url=http://www.onlamp.com/pub/a/php/2004/07/15/UpgradePHP5.html|publisher=O'Reilly|accessdate=2008-02-22|date=2004-07-15|author=Trachtenberg, Adam}}</ref> In 2008 PHP 5 became the only stable version under development. [[Late static binding]] had been missing from PHP and was added in version 5.3.<ref>{{cite web|url=http://www.digitalsandwich.com/archives/53-Late-Static-Binding-in-PHP.html|accessdate=2008-03-25|title=Late Static Binding in PHP|date=2006-02-23|publisher=Digital Sandwich}}</ref><ref>{{cite web|accessdate=2008-03-25|url=http://www.php.net/language.oop5.static|title=Static Keyword|publisher=The PHP Group}}</ref> |
On July 13, 2004, PHP 5 was released, powered by the new Zend Engine II.<ref name="about PHP"/> PHP 5 included new features such as improved support for [[object-oriented programming]], the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements.<ref>{{cite web|title=Why PHP 5 Rocks!|url=http://www.onlamp.com/pub/a/php/2004/07/15/UpgradePHP5.html|publisher=O'Reilly|accessdate=2008-02-22|date=2004-07-15|author=Trachtenberg, Adam}}</ref> In 2008 PHP 5 became the only stable version under development. [[Late static binding]] had been missing from PHP and was added in version 5.3.<ref>{{cite web|url=http://www.digitalsandwich.com/archives/53-Late-Static-Binding-in-PHP.html|accessdate=2008-03-25|title=Late Static Binding in PHP|date=2006-02-23|publisher=Digital Sandwich}}</ref><ref>{{cite web|accessdate=2008-03-25|url=http://www.php.net/language.oop5.static|title=Static Keyword|publisher=The PHP Group}}</ref> |
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Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative,<ref name="gophp5_projects">{{cite web | url=http://www.gophp5.org/projects|title=GoPHP5 |
Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative,<ref name="gophp5_projects">{{cite web | url=http://www.gophp5.org/projects|title=GoPHP5}}</ref> provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.<ref name="gophp5">{{cite web |url=http://gophp5.org/sites/gophp5.org/files/press_release.pdf |format=PDF |title=PHP projects join forces to Go PHP 5 |accessdate=2008-02-23 |work=GoPHP5 Press Release |author=GoPHP5}}</ref><ref>{{cite web|url=http://gophp5.org/|title=GoPHP5|publisher=GoPHP5|accessdate=2008-02-22}}</ref> |
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PHP interpreters are available on most existing [[32-bit]] and [[64-bit]] operating systems, either by building them from the PHP source code, or by using pre-built binaries.<ref>{{cite web |
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| url = //www.php.net/manual/en/install.php |
| url = http://www.php.net/manual/en/install.php |
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| title = PHP Installation and Configuration |
| title = PHP Installation and Configuration |
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| accessdate = 2013-10-29 |
| accessdate = 2013-10-29 |
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| |
| publisher = php.net |
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}}</ref> For the PHP versions 5.3 and 5.4, the only available [[Microsoft Windows]] binary distributions were 32-bit [[x86]] builds,<ref>{{cite web |
}}</ref> For the PHP versions 5.3 and 5.4, the only available [[Microsoft Windows]] binary distributions were 32-bit [[x86]] builds,<ref>{{cite web |
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| url = http://windows.php.net/download/#php-5.3 |
| url = http://windows.php.net/download/#php-5.3 |
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| title = PHP for Windows: Binaries and sources releases (5.3) |
| title = PHP for Windows: Binaries and sources releases (5.3) |
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| accessdate = 2013-10-29 |
| accessdate = 2013-10-29 |
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| |
| publisher = php.net |
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}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
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| url = http://windows.php.net/download/#php-5.4 |
| url = http://windows.php.net/download/#php-5.4 |
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| title = PHP for Windows: Binaries and sources releases (5.4) |
| title = PHP for Windows: Binaries and sources releases (5.4) |
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| accessdate = 2013-10-29 |
| accessdate = 2013-10-29 |
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| |
| publisher = php.net |
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}}</ref> requiring Windows 32-bit compatibility mode while using [[Internet Information Services]] (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit [[x86-64]] builds available for Microsoft Windows.<ref>{{cite web |
}}</ref> requiring Windows 32-bit compatibility mode while using [[Internet Information Services]] (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit [[x86-64]] builds available for Microsoft Windows.<ref>{{cite web |
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| url = http://windows.php.net/download/#php-5.5 |
| url = http://windows.php.net/download/#php-5.5 |
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| title = PHP for Windows: Binaries and sources releases (5.5) |
| title = PHP for Windows: Binaries and sources releases (5.5) |
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| accessdate = 2013-10-29 |
| accessdate = 2013-10-29 |
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| |
| publisher = php.net |
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}}</ref> |
}}</ref> |
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=== {{Anchor|PHP6-UNICODE}}PHP 6 and Unicode === |
=== {{Anchor|PHP6-UNICODE}}PHP 6 and Unicode === |
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PHP received mixed reviews due to lacking native [[Unicode]] support at the core language level.<ref>{{cite web |
PHP received mixed reviews due to lacking native [[Unicode]] support at the core language level.<ref>{{cite web |
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| url = //php.net/manual/en/language.types.string.php |
| url = http://php.net/manual/en/language.types.string.php |
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| title = Types: Strings |
| title = Types: Strings | work = PHP Manual |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
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| |
| publisher = PHP.net |
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}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
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| url = //www.php.net/manual/en/language.types.string.php#language.types.string.details |
| url = http://www.php.net/manual/en/language.types.string.php#language.types.string.details |
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| title = Details of the String Type |
| title = Details of the String Type | work = PHP Manual |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
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| |
| publisher = PHP.net |
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}}</ref> In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the [[International Components for Unicode]] (ICU) library, and representing text strings as [[UTF-16]] internally.<ref>{{cite web|url=http://marc.info/?l=php-internals&m=112365908921757&w=1|title=PHP Unicode support design document (mailing list post)|date=2005-08-10|accessdate=2014-02-09|author=Andrei Zmievski}}</ref> Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.<ref>{{cite web|url=http://news.php.net/php.internals/17668|title=PHP 5.5 or 6.0|accessdate=2014-02-09}}</ref> |
}}</ref> In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the [[International Components for Unicode]] (ICU) library, and representing text strings as [[UTF-16]] internally.<ref>{{cite web|url=http://marc.info/?l=php-internals&m=112365908921757&w=1|title=PHP Unicode support design document (mailing list post)|date=2005-08-10|accessdate=2014-02-09|author=Andrei Zmievski}}</ref> Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.<ref>{{cite web|url=http://news.php.net/php.internals/17668|title=PHP 5.5 or 6.0|accessdate=2014-02-09}}</ref> |
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However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project.<ref>{{cite web|title=The Good, the Bad, and the Ugly: What Happened to Unicode and PHP 6|url=http://www.slideshare.net/andreizm/the-good-the-bad-and-the-ugly-what-happened-to-unicode-and-php-6|accessdate=2014-02-09|author=Andrei Zmievski}}</ref> As a result, a PHP |
However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project.<ref>{{cite web|title=The Good, the Bad, and the Ugly: What Happened to Unicode and PHP 6|url=http://www.slideshare.net/andreizm/the-good-the-bad-and-the-ugly-what-happened-to-unicode-and-php-6|accessdate=2014-02-09|author=Andrei Zmievski}}</ref> As a result, a PHP 5.3 release was created in 2009, with many non-Unicode features back-ported from PHP 6, notably namespaces. In March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared containing most remaining non-Unicode features from PHP 6, such as traits and closure re-binding.<ref>{{cite web|url=http://news.php.net/php.internals/47120|title=PHP 6 (mailing list post)|accessdate=2014-02-07|date=2010-03-11|author=Rasmus Lerdorf}}</ref> Initial hopes were that a new plan would be formed for Unicode integration, but as of 2014 none has been adopted. |
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=== {{Anchor|NG|ZE3|PHP7}}PHP 7 === |
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During 2014 and 2015, a new major PHP version was developed, which was numbered PHP 7. The numbering of this version involved some debate.<ref>https://philsturgeon.uk/php/2014/07/23/neverending-muppet-debate-of-php-6-v-php-7/</ref> While the PHP 6 Unicode experiment had never been released, several articles and book titles referenced the PHP 6 name, which might have caused confusion if a new release were to reuse the name.<ref>{{cite web |title=RFC: Name of Next Release of PHP |url=https://wiki.php.net/rfc/php6 |date=2014-07-07 |accessdate=2014-07-15 |website=php.net}}</ref> After a vote, the name PHP 7 was chosen.<ref>{{cite web|title=Re: [PHP-DEV] [VOTE][RFC] Name of Next Release of PHP (again) |url=https://www.mail-archive.com/internals@lists.php.net/msg68598.html |date=2014-07-30 |accessdate=2014-07-30}}</ref> |
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=== {{Anchor|NG}}PHP 7 === |
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The foundation of PHP 7 is a PHP [[Branching (revision control)|branch]] that was originally dubbed ''PHP next generation'' (''phpng''). It was authored by Dmitry Stogov, Xinchen Hui and Nikita Popov,<ref>http://news.php.net/php.internals/73888</ref> it aimed at optimizing PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility.<ref>{{cite web |url=https://wiki.php.net/rfc/phpng |title=PHP: rfc:phpng |accessdate=16 December 2014 |website=php.net}}</ref> {{As of|2014|07|14}}, [[WordPress]]-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng are also expected to make it easier to improve performance in the future, as more compact data structures and other changes are seen as better suited for a successful migration to a [[Just-in-time compilation|just-in-time]] (JIT) compiler.<ref name="phpng">{{cite web|url=https://wiki.php.net/phpng |title=PHP: phpng |website=php.net |accessdate=2014-07-15}}</ref> Because of the significant changes, the reworked Zend Engine is called ''Zend Engine 3'', succeeding Zend Engine 2 used in PHP 5.<ref name="ZE2">{{cite web |url=https://github.com/php/php-src/commit/150dc69d6eee35738f505e925ee664c02060196d |website=github.com |date=2014-12-05 |accessdate=2014-12-05 |title=Merge branch 'ZendEngine3'}}</ref> |
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There was some dispute as to whether the next major version of PHP was to be called PHP 6 or PHP 7. While the PHP 6 unicode experiment had never been released, a number of articles and book titles referenced the old PHP 6 name, which might have caused confusion if a new release were to reuse the PHP 6 name.<ref>{{cite web |title=RFC: Name of Next Release of PHP |url=https://wiki.php.net/rfc/php6 |date=2014-07-07 |accessdate=2014-07-15}}</ref> After a vote, the name PHP 7 was chosen.<ref>{{cite web|title=Re: [PHP-DEV] [VOTE][RFC] Name of Next Release of PHP (again) |url=https://www.mail-archive.com/internals@lists.php.net/msg68598.html |date=2014-07-30 |accessdate=2014-07-30}}</ref> |
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Since {{date|2014-01-20}}, work has been underway on an experimental PHP [[Branching (revision control)|branch]] named ''PHPNG'' (''PHP Next Generation''), aimed at optimizing PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility. {{As of|2014|07|14}}, the main benchmark suite for the PHPNG project, which [[WordPress]] is used for, shows an almost 100% increase in performance.<ref>{{cite web|url=https://wiki.php.net/phpng |title=PHP: phpng |publisher=PHP.net |accessdate=2014-07-15}}</ref> PHPNG is intended by its authors to be the foundation of PHP 7.<ref>{{cite web|url=https://wiki.php.net/rfc/phpng|title=PHP RFC: Move the phpng branch into master|date=2014-07-20}}</ref> |
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Because of major internal changes in phpng, it must receive a new [[Software versioning|major version]] number of PHP, rather than a minor PHP 5 release, according to PHP's release process.<ref name="releaseprocess" /> Major versions of PHP are allowed to break backward-compatibility of code and therefore PHP 7 presented an opportunity for other improvements beyond phpng that require backward-compatibility breaks. In particular, it involved the following changes: |
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* Many fatal- or recoverable-level legacy PHP error mechanisms were replaced with modern object-oriented [[Exception (computer science)|exceptions]]<ref name="engine_exceptions" /> |
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* The syntax for variable dereferencing was reworked to be internally more consistent and complete, allowing the use of the operators ''->'', ''[]'', ''()'', ''{}'', and ''::'' with arbitrary meaningful left-hand-side expressions<ref name="uvs">{{cite web |url=https://wiki.php.net/rfc/uniform_variable_syntax |title=PHP RFC: Uniform Variable Syntax |date=2014-05-31 |accessdate=2014-07-30 |website=php.net}}</ref> |
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* Support for legacy PHP 4-style constructor methods was removed<ref>{{cite web|url=https://wiki.php.net/rfc/remove_php4_constructors|title=PHP RFC: Remove PHP 4 Constructors|accessdate=2015-05-21|website=php.net}}</ref> |
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* The behavior of the [[Foreach loop|''foreach'' statement]] was changed to be more predictable<ref>{{cite web|url=https://wiki.php.net/rfc/php7_foreach|title=PHP RFC: Fix "foreach" behavior|accessdate=2015-05-21|website=php.net}}</ref> |
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* Constructors for the few classes built-in to PHP which returned null upon failure were changed to throw an exception instead, for consistency<ref>{{cite web|url=https://wiki.php.net/rfc/internal_constructor_behaviour|title=PHP RFC: Constructor behaviour of internal classes|accessdate=2015-05-21|website=php.net}}</ref> |
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* Several unmaintained or deprecated [[server application programming interface]]s (SAPIs) and extensions were removed from the PHP core, most notably the legacy ''mysql'' extension<ref>{{cite web|url=https://wiki.php.net/rfc/removal_of_dead_sapis_and_exts|title=PHP RFC: Removal of dead or not yet PHP7 ported SAPIs and extensions|accessdate=2015-05-21|website=php.net}}</ref> |
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* The behavior of the ''list()'' operator was changed to remove support for strings<ref>{{cite web|url=https://wiki.php.net/rfc/fix_list_behavior_inconsistency|title=PHP RFC: Fix list() behavior inconsistency|accessdate=2015-05-21|website=php.net}}</ref> |
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* Support for legacy ASP-style PHP code delimiters (''<%'' and ''%>'', ''<script language=php>'' and ''</script>'') was removed<ref>{{cite web|url=https://wiki.php.net/rfc/remove_alternative_php_tags|title=PHP RFC: Remove alternative PHP tags|accessdate=2015-05-21|website=php.net}}</ref> |
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* An oversight allowing a [[switch statement]] to have multiple ''default'' clauses was fixed<ref>{{cite web|url=https://wiki.php.net/rfc/switch.default.multiple|title=PHP RFC: Make defining multiple default cases in a switch a syntax error|accessdate=2015-05-21|website=php.net}}</ref> |
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* Support for hexadecimal number support in some implicit conversions from strings to number types was removed<ref>{{cite web|url=https://wiki.php.net/rfc/remove_hex_support_in_numeric_strings|title=PHP RFC: Remove hex support in numeric strings|accessdate=2015-05-21|website=php.net}}</ref> |
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* The [[left-shift operator|left-shift]] and [[right-shift operator|right-shift]] operators were changed to behave more consistently across platforms<ref name="integer_semantics">{{cite web|url=https://wiki.php.net/rfc/integer_semantics|title=PHP RFC: Integer Semantics|accessdate=2015-05-21|website=php.net}}</ref> |
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* Conversions between integers and floating point numbers were tightened and implemented more consistently across platforms<ref name="integer_semantics" /><ref>{{cite web|url=https://wiki.php.net/rfc/zpp_fail_on_overflow|title=PHP RFC: ZPP Failure on Overflow|accessdate=2015-05-21|website=php.net}}</ref> |
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PHP |
PHP 7 will contain an improved variable syntax which is internally consistent and complete, what is a long-standing issue in PHP. This will allow use of <tt>-></tt>, <tt>[]</tt>, <tt>()</tt>, <tt>{}</tt>, and <tt>::</tt> operators with arbitrary meaningful left-hand-side expressions. The current implementation of this change has been made on top of the PHPNG branch.<ref>{{cite web|url=https://wiki.php.net/rfc/uniform_variable_syntax |title=PHP RFC: Uniform Variable Syntax |date=2014-05-31 |accessdate=2014-07-30}}</ref> |
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=== Release history === |
=== Release history === |
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! Version |
! Version |
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! style="min-width: 10em;" | Release date |
! style="min-width: 10em;" | Release date |
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! style="min-width: 10em;" | Supported until<ref |
! style="min-width: 10em;" | Supported until<ref>{{cite web|url=http://php.net/eol.php |title=Unsupported Branches |publisher=PHP |accessdate=2013-08-16}}</ref> |
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! Notes |
! Notes |
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| style="background:salmon;"| 3.0 |
| style="background:salmon;"| 3.0 |
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| {{Date|1998-06-06}} |
| {{Date|1998-06-06}} |
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| {{Date|2000-10-20}} |
| {{Date|2000-10-20}} |
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| Development moves from one person to multiple developers. Zeev Suraski and Andi Gutmans rewrite the base for this version.<ref name="about PHP"/> |
| Development moves from one person to multiple developers. Zeev Suraski and Andi Gutmans rewrite the base for this version.<ref name="about PHP"/> |
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|- |
|- |
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| style="background:salmon;"| 4.0 |
| style="background:salmon;"| 4.0 |
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| {{Date|2000-05-22}} |
| {{Date|2000-05-22}} |
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| {{Date|2001- |
| {{Date|2001-01-23}} |
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| Added more advanced two-stage parse/execute tag-parsing system called the Zend engine.<ref name="php4changelog">{{cite web|title=PHP: PHP 4 ChangeLog|url=http://www.php.net/ChangeLog-4.php|publisher=The PHP Group|accessdate=2008-02-22|date=2008-01-03}}</ref> |
| Added more advanced two-stage parse/execute tag-parsing system called the Zend engine.<ref name="php4changelog">{{cite web|title=PHP: PHP 4 ChangeLog|url=http://www.php.net/ChangeLog-4.php|publisher=The PHP Group|accessdate=2008-02-22|date=2008-01-03}}</ref> |
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|- |
|- |
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| style="background:salmon;"| 4.1 |
| style="background:salmon;"| 4.1 |
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| {{Date|2001-12-10}} |
| {{Date|2001-12-10}} |
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| {{Date|2002-03-12}} |
| {{Date|2002-03-12}} |
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| Introduced 'superglobals' (<code>$_GET</code>, <code>$_POST</code>, <code>$_SESSION</code>, etc.)<ref name="php4changelog" /> |
| Introduced 'superglobals' (<code>$_GET</code>, <code>$_POST</code>, <code>$_SESSION</code>, etc.)<ref name="php4changelog" /> |
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|- |
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| style="background:salmon;"| 4.2 |
| style="background:salmon;"| 4.2 |
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| {{Date|2002-04-22}} |
| {{Date|2002-04-22}} |
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| {{Date|2002-09-06}} |
| {{Date|2002-09-06}} |
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| Disabled <code>register_globals</code> by default. Data received over the network is not inserted directly into the [[global variable|global]] namespace anymore, closing possible security holes in applications.<ref name="php4changelog" /> |
| Disabled <code>register_globals</code> by default. Data received over the network is not inserted directly into the [[global variable|global]] namespace anymore, closing possible security holes in applications.<ref name="php4changelog" /> |
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|- |
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| style="background:salmon;"| 4.3 |
| style="background:salmon;"| 4.3 |
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| {{Date|2002-12-27}} |
| {{Date|2002-12-27}} |
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| {{Date|2005-03-31}} |
| {{Date|2005-03-31}} |
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| Introduced the [[command-line interface]] (CLI), to supplement the CGI.<ref name="php4changelog" /><ref name="phpclidocs">{{cite web|title= Using PHP from the command line | work = PHP Manual|url=http://php.net/manual/en/features.commandline.php|publisher=The PHP Group|accessdate=2009-09-11}}</ref> |
| Introduced the [[command-line interface]] (CLI), to supplement the CGI.<ref name="php4changelog" /><ref name="phpclidocs">{{cite web|title= Using PHP from the command line | work = PHP Manual|url=http://php.net/manual/en/features.commandline.php|publisher=The PHP Group|accessdate=2009-09-11}}</ref> |
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|- |
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| style="background:salmon;"| 4.4 |
| style="background:salmon;"| 4.4 |
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| {{Date|2005-07-11}} |
| {{Date|2005-07-11}} |
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| {{Date|2008-08-07}} |
| {{Date|2008-08-07}} |
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|Fixed a memory corruption bug, which required breaking binary compatibility with extensions compiled against PHP version 4.3.x.<ref name="php44announcement">{{cite web|title=PHP 4.4.0 Release Announcement|work=PHP Mannual|url=http://php.net/releases/4_4_0.php|publisher=The PHP Group|accessdate=2013-11-24}}</ref> |
|Fixed a memory corruption bug, which required breaking binary compatibility with extensions compiled against PHP version 4.3.x.<ref name="php44announcement">{{cite web|title=PHP 4.4.0 Release Announcement|work=PHP Mannual|url=http://php.net/releases/4_4_0.php|publisher=The PHP Group|accessdate=2013-11-24}}</ref> |
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|- |
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| style="background:salmon;"| 5.0 |
| style="background:salmon;"| 5.0 |
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| {{Date|2004-07-13}} |
| {{Date|2004-07-13}} |
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| {{Date|2005-09-05}} |
| {{Date|2005-09-05}} |
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|Zend Engine II with a new object model.<ref name="php5changelog">{{cite web|title=PHP: PHP 5 ChangeLog|url=http://www.php.net/ChangeLog-5.php|publisher=The PHP Group|accessdate=2008-02-22|date=2007-11-08}}</ref> |
|Zend Engine II with a new object model.<ref name="php5changelog">{{cite web|title=PHP: PHP 5 ChangeLog|url=http://www.php.net/ChangeLog-5.php|publisher=The PHP Group|accessdate=2008-02-22|date=2007-11-08}}</ref> |
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| style="background:salmon;"| 5.1 |
| style="background:salmon;"| 5.1 |
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| {{Date|2005-11-24}} |
| {{Date|2005-11-24}} |
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| {{Date|2006-08-24}} |
| {{Date|2006-08-24}} |
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| Performance improvements with introduction of compiler variables in re-engineered PHP Engine.<ref name="php5changelog" /> Added PHP Data Objects (PDO) as a consistent interface for accessing databases.<ref name="phpPdoDocs">{{cite web|title=PHP manual: PDO|url=http://php.net/manual/en/intro.pdo.php|publisher=The PHP Group|accessdate=2011-11-15|date=2011-11-15}}</ref> |
| Performance improvements with introduction of compiler variables in re-engineered PHP Engine.<ref name="php5changelog" /> Added PHP Data Objects (PDO) as a consistent interface for accessing databases.<ref name="phpPdoDocs">{{cite web|title=PHP manual: PDO|url=http://www.php.net/manual/en/intro.pdo.php|publisher=The PHP Group|accessdate=2011-11-15|date=2011-11-15}}</ref> |
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| style="background:salmon;"| 5.2 |
| style="background:salmon;"| 5.2 |
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| {{Date|2006-11-02}} |
| {{Date|2006-11-02}} |
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| {{Date|2011-01-06}} |
| {{Date|2011-01-06}} |
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| Enabled the filter extension by default. Native [[JSON]] support.<ref name="php5changelog" /> |
| Enabled the filter extension by default. Native [[JSON]] support.<ref name="php5changelog" /> |
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| style="background: |
| style="background:#FCED77;"| 5.3 |
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| {{Date|2009-06-30}} |
| {{Date|2009-06-30}} |
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| 14 August 2014<ref>{{cite web|url=http://marc.info/?l=php-internals&m=140605526629324&w=2 |title=[PHP-DEV] Re: 5.3 final release |publisher=PHP |accessdate=2014-07-23}}</ref> |
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| {{Date|2014-08-14}}<ref name="eol" /> |
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| [[Namespace]] support; [[name binding|late static bindings]], |
| [[Namespace]] support; [[name binding|late static bindings]], Jump label (limited [[goto]]), Native [[closure (computer science)|closures]], Native PHP archives (phar), [[garbage collection (computer science)|garbage collection]] for circular references, improved [[Microsoft Windows|Windows]] support, sqlite3, mysqlnd as a replacement for libmysql as underlying library for the extensions that work with [[MySQL]], fileinfo as a replacement for mime_magic for better [[MIME]] support, the Internationalization extension, and deprecation of ereg extension. |
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|- |
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| style="background: |
| style="background:#a0e75a;"| 5.4 |
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| {{Date|2012-03-01}} |
| {{Date|2012-03-01}} |
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| {{Date|2015- |
| {{Date|2015-03-01}}<ref name="releaseprocess"/> |
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| [[trait (computer programming)|Trait]] support, short array syntax support. Removed items: <code>register_globals</code>, <code>safe_mode</code>, <code>allow_call_time_pass_reference</code>, <code>session_register()</code>, <code>session_unregister()</code> and <code>session_is_registered()</code>. Built-in web server.<ref>{{cite web|url=http://php.net/manual/en/features.commandline.webserver.php |title=Built-in web server |accessdate=March 26, 2012}}</ref> Several improvements to existing features, performance and reduced memory requirements. |
| [[trait (computer programming)|Trait]] support, short array syntax support. Removed items: <code>register_globals</code>, <code>safe_mode</code>, <code>allow_call_time_pass_reference</code>, <code>session_register()</code>, <code>session_unregister()</code> and <code>session_is_registered()</code>. Built-in web server.<ref>{{cite web|url=http://php.net/manual/en/features.commandline.webserver.php |title=Built-in web server |accessdate=March 26, 2012}}</ref> Several improvements to existing features, performance and reduced memory requirements. |
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| style="background:# |
| style="background:#a0e75a;"| 5.5 |
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| {{Date|2013-06-20}} |
| {{Date|2013-06-20}} |
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| {{Date|2016-06-20}}<ref name="releaseprocess"/> |
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| 10 July 2016<ref name="supportedversions">{{cite web|url=http://php.net/supported-versions.php |title=Supported Versions |website=php.net |accessdate=2015-12-02}}</ref> |
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| Support for [[Generator (computer programming)|generators]], <code>finally</code> blocks for exceptions handling, OpCache (based on Zend Optimizer+) bundled in official distribution.<ref name="55changes">{{cite web|title=PHP 5.5.0 changes|url=http:// |
| Support for [[Generator (computer programming)|generators]], <code>finally</code> blocks for exceptions handling, OpCache (based on Zend Optimizer+) bundled in official distribution.<ref name="55changes">{{cite web|title=PHP 5.5.0 changes|url=http://mildcoder.com/what-is-new-in-php-5-5-0/|accessdate=2013-06-20}}</ref> |
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| style="background: |
| style="background:skyBlue;"| 5.6 |
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| No date set |
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| {{Date|2014-08-28}} |
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| {{Date|2018-12-31}}<ref name="supportedversions"/> |
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| Constant scalar expressions, [[variadic function]]s, argument unpacking, new exponentiation operator, extensions of the <tt>use</tt> statement for functions and constants, new <tt>phpdbg</tt> debugger as a SAPI module, and other smaller improvements.<ref name="56changes">{{cite web |title=Migrating from PHP 5.5.x to PHP 5.6.x |url=http://www.php.net/manual/en/migration56.new-features.php |accessdate=2014-03-24 |website=php.net}}</ref> |
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|- |
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| style="background:"| 6.x |
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| {{n/a|Not released}} |
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| {{n/a}} |
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| Abandoned version of PHP that planned to include native Unicode support.<ref>{{cite web|url=https://lwn.net/Articles/379909/|title=Resetting PHP 6|quote=There have been books on the shelves purporting to cover PHP 6 since at least 2008. But, in March 2010, the PHP 6 release is not out - in fact, it is not even close to out. Recent events suggest that PHP 6 will not be released before 2011 - if, indeed, it is released at all.}}</ref><ref>{{cite web|url=http://www.infoworld.com/article/2841561/php/php-7-moves-full-speed-ahead.html|title=PHP 7 moves full speed ahead|quote=Recent versions of PHP have been part of the 5.x release series, but there will be no PHP 6. “We’re going to skip [version] 6 because years ago, we had plans for a 6 but those plans were very different from what we’re doing now,” Gutmans said. Going right to version 7 avoids confusion.}}</ref> |
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| style="background:#a0e75a;"| 7.0 |
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| {{Date|2015-12-03}}<ref name=php7final /> |
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| {{Date|2018-12-03}}<ref name="releaseprocess"/> |
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| Zend Engine 3 (performance improvements<ref name="phpng" /> and 64-bit integer support on Windows<ref>{{cite web|url=https://wiki.php.net/rfc/size_t_and_int64_next|title=PHP: rfc:size_t_and_int64_next|website=php.net|accessdate=16 December 2014}}</ref>), uniform variable syntax,<ref name="uvs" /> [[Abstract Syntax Tree|AST]]-based compilation process,<ref>{{cite web|url=https://wiki.php.net/rfc/abstract_syntax_tree|title=PHP: rfc:abstract_syntax_tree|website=php.net|accessdate=16 December 2014}}</ref> added <code>Closure::call()</code>,<ref>{{cite web|url=https://wiki.php.net/rfc/closure_apply|title=PHP: rfc:closure_apply|website=php.net|accessdate=16 December 2014}}</ref> bitwise shift consistency across platforms,<ref>{{cite web|url=https://wiki.php.net/rfc/integer_semantics|title=PHP: rfc:integer_semantics|website=php.net|accessdate=16 December 2014}}</ref> <code>??</code> ([[Null coalescing operator|null coalesce]]) operator,<ref>{{cite web|url=https://wiki.php.net/rfc/isset_ternary|title=PHP: rfc:isset_ternary|website=php.net|accessdate=16 December 2014}}</ref> [[Unicode]] codepoint [[String literal#Escape sequences|escape syntax]],<ref>{{cite web|url=https://wiki.php.net/rfc/unicode_escape|title=RFC: Unicode Codepoint Escape Syntax|date=2014-11-24|accessdate=2014-12-19}}</ref> return type declarations,<ref name="return-types" /> scalar type (integer, float, string and boolean) declarations,<ref name="scalar-types" /> <code><=></code> "spaceship" [[three-way comparison]] operator,<ref>{{cite web|url=https://wiki.php.net/rfc/combined-comparison-operator|title=Combined Comparison (Spaceship) Operator|website=php.net|accessdate=2015-05-21}}</ref> [[Generator (computer programming)|generator]] delegation,<ref>{{cite web|url=https://wiki.php.net/rfc/generator-delegation|title=PHP RFC: Generator Delegation|accessdate=2015-05-21|website=php.net}}</ref> [[anonymous class]]es,<ref>{{cite web|url=https://wiki.php.net/rfc/anonymous_classes|title=PHP RFC: Anonymous Classes|accessdate=2015-05-21|website=php.net}}</ref> simpler and more consistently available [[CSPRNG]] API,<ref>{{cite web|url=https://wiki.php.net/rfc/easy_userland_csprng|title=PHP RFC: Easy User-land CSPRNG|accessdate=2015-05-21|website=php.net}}</ref> replacement of many remaining internal PHP "errors" with the more modern [[Exception (computer science)|exceptions]],<ref name="engine_exceptions">{{cite web|url=https://wiki.php.net/rfc/engine_exceptions_for_php7|title=PHP RFC: Exceptions in the engine (for PHP 7)|accessdate=2015-05-21|website=php.net}}</ref> and shorthand syntax for importing multiple items from a namespace.<ref>{{cite web|url=https://wiki.php.net/rfc/group_use_declarations|title=PHP RFC: Group Use Declarations|accessdate=2015-05-21|website=php.net}}</ref> |
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| style="background:skyBlue;"| 7.1 |
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| 2016 |
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| 3 years after release<ref name="releaseprocess"/> |
| 3 years after release<ref name="releaseprocess"/> |
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| Constant scalar expressions, [[variadic function]]s, argument unpacking, new exponentiation operator, extensions of the <tt>use</tt> statement for functions and constants, new <tt>phpdbg</tt> debugger as a SAPI module, and other smaller improvements.<ref name="56changes">{{cite web |title=Migrating from PHP 5.5.x to PHP 5.6.x |url=http://www.php.net/manual/en/migration56.new-features.php |accessdate=2014-03-24 |publisher=php.net}}</ref> |
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| [[Void type|void return type]],<ref>{{cite web|url=http://wiki.php.net/rfc/void_return_type|title=PHP: rfc:void_return_type|website=php.net|date=2015-11-09|accessdate=2015-11-14}}</ref> class constant [[information hiding|visibility modifiers]]<ref>{{cite web|url=https://wiki.php.net/rfc/class_const_visibility|title=PHP: rfc:class_constant_visibility|website=php.net|date=2015-10-27|accessdate=2015-12-08}}</ref> |
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Beginning on June 28, 2011, the PHP Group |
Beginning on June 28, 2011, the PHP Group began following a timeline for when new versions of PHP will be released.<ref name="releaseprocess">{{cite web|title=PHP: Release Process|url=https://wiki.php.net/rfc/releaseprocess|accessdate=2013-10-06|date=2011-06-20}}</ref> Under this timeline, at least one release should occur every month. Once per year, a minor release should occur which can include new features. Every minor release should at least have 2 years of security and bug fixes, followed by at least 1 year of only security fixes, for a total of a 3 year release process for every minor release. No new features (unless small and self-contained) will be introduced into a minor release during the 3-year release process. |
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== {{Anchor|ELEPHPANT}}Mascot == |
== {{Anchor|ELEPHPANT}}Mascot == |
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The mascot of the PHP project is the ''elePHPant'', a blue [[elephant]] with the PHP logo on its side |
The mascot of the PHP project is the ''elePHPant'', a blue (sometimes differently colored when in [[plush toy]] form) [[elephant]] with the PHP logo on its side.{{citation needed|date=July 2014}} |
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<gallery widths=170 heights=110> |
<gallery widths=170 heights=110> |
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File:Elephpant.png|The |
File:Elephpant.png|The ElePHPant, PHP mascot |
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File:ElePHPant studying notes from SugarCon 2007.jpg|A [[plush toy]] elePHPant |
File:ElePHPant studying notes from SugarCon 2007.jpg|A [[plush toy]] elePHPant |
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</gallery> |
</gallery> |
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== Syntax == |
== Syntax == |
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{{copy edit|section|for=syntax highlighting|date=December 2015}} |
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{{Main|PHP syntax and semantics}} |
{{Main|PHP syntax and semantics}} |
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The following [[ |
The following [[Hello world program]] is written in PHP code embedded in an [[HTML]] document: |
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<source lang= |
<source lang="php"> |
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<!DOCTYPE html> |
<!DOCTYPE html> |
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<html> |
<html> |
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Line 280: | Line 249: | ||
</source> |
</source> |
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However, as |
However, as PHP does not need to be embedded in HTML or used with a web server, the simplest version of a Hello World program can be written like this, with the closing tag omitted as preferred in files containing pure PHP code<ref>{{cite web|url=http://www.php.net/manual/en/language.basic-syntax.phptags.php |title=tags - Manual |publisher=PHP |accessdate=2014-02-17}}</ref> (prior to PHP 5.4.0, this short syntax for <tt>echo()</tt> only works with the <tt>short_open_tag</tt> configuration setting enabled, while for PHP 5.4.0 and later it is always available):<ref>{{cite web|url=http://www.php.net/echo |title=echo - Manual |publisher=PHP |accessdate=2014-02-17}}</ref><ref>{{cite web|url=http://www.php.net/manual/en/ini.core.php#ini.short-open-tag |title=Description of core php.ini directives - Manual |publisher=PHP |date=2002-03-17 |accessdate=2014-02-17}}</ref><ref name="rfc-shortags">{{cite web|url=http://wiki.php.net/rfc/shortags |title=PHP: rfc:shortags |publisher=php.net |date=2008-04-03 |accessdate=2014-05-08}}</ref> |
||
<source lang="php"> |
|||
<?='Hello world'; |
|||
<?= 'Hello world'; |
|||
</source> |
|||
The PHP interpreter only executes PHP code within its [[delimiter]]s. Anything outside its delimiters is not processed by PHP |
The PHP interpreter only executes PHP code within its [[delimiter]]s. Anything outside its delimiters is not processed by PHP (although non-PHP text is still subject to [[control structure]]s described in PHP code). The most common delimiters are <code><?php</code> to open and <code>?></code> to close PHP sections. <code><script language="php"></code> and <code></script></code> delimiters are also available, as are the shortened forms <code><?</code> or <code><?=</code> (which is used to echo back a [[string (computer science)|string]] or [[variable (programming)|variable]]) and <code>?></code> as well as [[Active Server Pages|ASP]]-style short forms <code><%</code> or <code><%=</code> and <code>%></code>. Short delimiters make script files less portable, since support for them can be disabled in the local PHP configuration, and they are therefore discouraged.<ref name="rfc-shortags" /><ref name="basic syntax">{{cite web|title=PHP: Basic syntax|url=http://www.php.net/manual/en/language.basic-syntax.php|publisher=The PHP Group|accessdate=2008-02-22}}</ref> The purpose of all these delimiters is to separate PHP code from non-PHP code, including HTML.<ref>{{cite web|accessdate=2008-02-25|url=http://www.php.net/manual/en/tutorial.firstpage.php|title=Your first PHP-enabled page |publisher=The PHP Group}}</ref> |
||
The first form of delimiters, |
The first form of delimiters, <code><?php</code> and <code>?></code>, in [[XHTML]] and other [[XML]] documents, creates correctly formed XML "processing instructions".<ref>{{cite web | url = http://www.w3.org/TR/2008/REC-xml-20081126/#sec-pi | title = Processing Instructions | work = Extensible Markup Language (XML) 1.0 (Fifth Edition) | publisher = W3C | date = 26 November 2008 | last = Bray | first = Tim |author2=et al | accessdate = 2009-06-18}}</ref> This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML. |
||
{{Anchor|TYPE-HINTING}} |
{{Anchor|TYPE-HINTING}} |
||
Variables are prefixed with a [[dollar sign|dollar symbol]], and a [[primitive type|type]] does not need to be specified in advance. PHP 5 introduced ''type hinting'' that allows functions to force their parameters to be objects of a specific class, arrays, interfaces or [[callback function]]s. However |
Variables are prefixed with a [[dollar sign|dollar symbol]], and a [[primitive type|type]] does not need to be specified in advance. PHP 5 introduced ''type hinting'' that allows functions to force their parameters to be objects of a specific class, arrays, interfaces or [[callback function]]s. However, type hints can not be used with scalar types such as integer or string.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/language.oop5.typehinting.php |
|||
| title = Type hinting | work = PHP manual |
|||
| accessdate = 2014-06-12 |
|||
| publisher = php.net |
|||
}}</ref> |
|||
Unlike function and class names, variable names are case sensitive. Both double-quoted ("") and [[heredoc]] strings provide the ability to interpolate a variable's value into the string.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.variables.php|title=Variables |publisher=The PHP Group}}</ref> PHP treats [[newline]]s as [[whitespace character|whitespace]] in the manner of a [[free-form language]], and statements are terminated by a semicolon.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/basic-syntax.instruction-separation|title=Instruction separation |publisher=The PHP Group}}</ref> PHP has three types of [[comparison of programming languages (syntax)#Comments|comment syntax]]: <code>/* */</code> marks block and inline comments; <code>//</code> as well as <code>#</code> are used for one-line comments.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.basic-syntax.comments.php|title=Comments |publisher=The PHP Group}}</ref> The < |
Unlike function and class names, variable names are case sensitive. Both double-quoted (<code>""</code>) and [[heredoc]] strings provide the ability to interpolate a variable's value into the string.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.variables.php|title=Variables |publisher=The PHP Group}}</ref> PHP treats [[newline]]s as [[whitespace character|whitespace]] in the manner of a [[free-form language]] (except when inside string quotes), and statements are terminated by a semicolon.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/basic-syntax.instruction-separation|title=Instruction separation |publisher=The PHP Group}}</ref> PHP has three types of [[comparison of programming languages (syntax)#Comments|comment syntax]]: <code>/* */</code> marks block and inline comments; <code>//</code> as well as <code>#</code> are used for one-line comments.<ref>{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.basic-syntax.comments.php|title=Comments |publisher=The PHP Group}}</ref> The <tt>echo</tt> statement is one of several facilities PHP provides to output text, ''e.g.'', to a web browser. |
||
In terms of keywords and language syntax, PHP is similar to the C style syntax. ''if'' conditions, ''for'' and ''while'' loops, and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl. |
In terms of keywords and language syntax, PHP is similar to most high level languages that follow the C style syntax. <code>''if''</code> conditions, <code>''for''</code> and <code>''while''</code> loops, and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl. |
||
=== Data types === |
=== Data types === |
||
Line 300: | Line 276: | ||
[[Floating point]] numbers are also stored in a platform-specific range. They can be specified using floating point notation, or two forms of [[scientific notation]].<ref name="types">{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.types.php|title=Types |publisher=The PHP Group}}</ref> PHP has a native [[Boolean datatype|Boolean]] type that is similar to the native Boolean types in [[Java (programming language)|Java]] and [[C++]]. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in [[Perl]] and C++.<ref name="types" /> |
[[Floating point]] numbers are also stored in a platform-specific range. They can be specified using floating point notation, or two forms of [[scientific notation]].<ref name="types">{{cite web|accessdate=2008-03-16|url=http://www.php.net/manual/en/language.types.php|title=Types |publisher=The PHP Group}}</ref> PHP has a native [[Boolean datatype|Boolean]] type that is similar to the native Boolean types in [[Java (programming language)|Java]] and [[C++]]. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in [[Perl]] and C++.<ref name="types" /> |
||
The null data type represents a variable that has no value; |
The null data type represents a variable that has no value; ''NULL'' is the only allowed value for this data type.<ref name="types" /> |
||
Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources.<ref name="types" /> |
Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources.<ref name="types" /> |
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Line 306: | Line 282: | ||
Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in [[hash table|hashes]] with both keys and values, and the two can be intermingled.<ref name="types" /> PHP also supports [[string (computing)|strings]], which can be used with single quotes, double quotes, nowdoc or [[heredoc]] syntax.<ref>{{cite web|accessdate=2008-03-21|url=http://www.php.net/manual/en/language.types.string.php|title=Strings |publisher=The PHP Group}}</ref> |
Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in [[hash table|hashes]] with both keys and values, and the two can be intermingled.<ref name="types" /> PHP also supports [[string (computing)|strings]], which can be used with single quotes, double quotes, nowdoc or [[heredoc]] syntax.<ref>{{cite web|accessdate=2008-03-21|url=http://www.php.net/manual/en/language.types.string.php|title=Strings |publisher=The PHP Group}}</ref> |
||
The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.<ref>{{cite web | url = http://www.php.net/spl | title = SPL |
The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.<ref>{{cite web | url = http://www.php.net/spl | title = SPL — StandardPHPLibrary | date = March 16, 2009 | publisher = PHP.net | accessdate = 2009-03-16}}</ref> |
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=== Functions === |
=== Functions === |
||
PHP |
PHP has hundreds of functions provided by the core language functionality and thousands more available via various extensions; these functions are well documented in the online PHP documentation.<ref name="functions" /> However, the built-in library has a wide variety of naming conventions and associated inconsistencies, as described under [[#ORGANIC|history]] above. |
||
Additional functions can be defined by the developer: |
|||
<pre> |
|||
<source lang="php"> |
|||
function myAge($birthYear) { // defines a function, this one is named "myAge" |
|||
function myAge($birthYear) // defines a function, this one is named "myAge" |
|||
{ |
|||
return $yearsOld . ' year' . ($yearsOld != 1 ? 's' : ''); // returns the age in a descriptive form |
|||
$yearsOld = date('Y') - $birthYear; // calculates the age |
|||
return $yearsOld . ' year' . ($yearsOld != 1 ? 's' : ''); // returns the age in a descriptive form |
|||
} |
} |
||
echo 'I am currently ' . myAge(1981) . ' old.'; // outputs the text concatenated |
echo 'I am currently ' . myAge(1981) . ' old.'; // outputs the text concatenated |
||
// with the return value of myAge() |
// with the return value of myAge() |
||
// As the result of this syntax, myAge() is called. |
// As the result of this syntax, myAge() is called. |
||
// In 2014, the output of this sample program will be 'I am currently 33 years old.' |
|||
</pre> |
|||
</source> |
|||
In {{CURRENTYEAR}}, the output of the above sample program is 'I am currently {{#expr: {{CURRENTYEAR}} - 1981 }} years old.' |
|||
In |
In PHP, normal functions are not [[first-class function|first-class]] and can only be referenced by their name directly, or dynamically by a variable containing the name of the function (referred to as "variable functions"). User-defined functions can be created at any time without being [[Function prototype|prototyped]].<ref name="functions">{{cite web |
||
| url = http://www.php.net/manual/en/functions.user-defined.php |
| url = http://www.php.net/manual/en/functions.user-defined.php |
||
| title = User-defined functions |
| title = User-defined functions | work = PHP manual |
||
| date = 2014-07-04 | accessdate = 2014-07-07 |
| date = 2014-07-04 | accessdate = 2014-07-07 |
||
| |
| publisher = php.net |
||
}}</ref><ref name="variable-functions">{{cite web |
}}</ref><ref name="variable-functions">{{cite web |
||
| url = http://www.php.net/manual/en/functions.variable-functions.php |
| url = http://www.php.net/manual/en/functions.variable-functions.php |
||
| title = Variable functions |
| title = Variable functions | work = PHP manual |
||
| date = 2014-07-04 | accessdate = 2014-07-07 |
| date = 2014-07-04 | accessdate = 2014-07-07 |
||
| |
| publisher = php.net |
||
}}</ref> Functions |
}}</ref> Functions can be defined inside code blocks, permitting a [[dynamic dispatch|run-time decision]] as to whether or not a function should be defined. Function calls must use parentheses, with the exception of zero-argument class [[constructor (computer science)|constructor]] functions called with the PHP <code>new</code> operator, where parentheses are optional. |
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Until PHP 5.3, support for [[anonymous functions]] |
Until PHP 5.3, support for true [[anonymous functions]] or [[Closure (computer science)|closures]] did not exist in PHP. While <code>create_function()</code> exists since PHP 4.0.1, it is merely a thin wrapper around <code>eval()</code> that allows normal PHP functions to be created during program execution.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/function.create-function.php |
| url = http://www.php.net/manual/en/function.create-function.php |
||
| title = create_function() |
| title = create_function() | work = PHP manual |
||
| date = 2014-07-04 | accessdate = 2014-07-07 |
| date = 2014-07-04 | accessdate = 2014-07-07 |
||
| |
| publisher = php.net |
||
}}</ref> Also, support for variable functions allows normal PHP functions to be used, for example, as [[Callback function|callbacks]] or within [[function table]]s.<ref name="variable-functions" /> PHP 5.3 added support for closures, which are true anonymous, first-class functions,<ref>{{cite web |
|||
}}</ref> PHP 5.3 added syntax to define an anonymous function or "closure"<ref>{{cite web |
|||
| url = http://www.php.net/manual/en/functions.anonymous.php |
| url = http://www.php.net/manual/en/functions.anonymous.php |
||
| title = Anonymous functions |
| title = Anonymous functions | work = PHP manual |
||
| date = 2014-07-04 | accessdate = 2014-07-07 |
| date = 2014-07-04 | accessdate = 2014-07-07 |
||
| |
| publisher = php.net |
||
}}</ref> |
}}</ref> whose syntax can be seen in the following example: |
||
<source lang="php"> |
|||
<pre> |
|||
function getAdder($x) |
function getAdder($x) |
||
{ |
|||
return function($y) use ($x) |
return function($y) use ($x) |
||
{ |
|||
return $x + $y; |
return $x + $y; |
||
}; |
}; |
||
Line 358: | Line 337: | ||
$adder = getAdder(8); |
$adder = getAdder(8); |
||
echo $adder(2); // prints "10" |
echo $adder(2); // prints "10" |
||
</ |
</source> |
||
In the example above, <code>getAdder()</code> function creates a closure using passed argument <code>$x</code> (the keyword <code>use</code> imports a variable from the lexical context), which takes an additional argument <code>$y</code>, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as a parameter to other functions, etc.<ref>{{cite web |
In the example above, <code>getAdder()</code> function creates a closure using passed argument <code>$x</code> (the keyword <code>use</code> imports a variable from the lexical context), which takes an additional argument <code>$y</code>, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as a parameter to other functions, etc.<ref>{{cite web |
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Line 365: | Line 344: | ||
| date = 2008-07-01 | accessdate = 2014-07-07 |
| date = 2008-07-01 | accessdate = 2014-07-07 |
||
| author1 = Christian Seiler | author2 = Dmitry Stogov |
| author1 = Christian Seiler | author2 = Dmitry Stogov |
||
| |
| publisher = php.net |
||
}}</ref> |
}}</ref> |
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The <code>[[goto]]</code> flow control statement is used as in the following example: |
|||
Unusually for a dynamically typed language, PHP supports type declarations on function parameters, which are enforced at runtime. This has been supported for classes and interfaces since PHP 5.0, for arrays since PHP 5.1, for "callables" since PHP 5.4, and scalar (integer, float, string and boolean) types since PHP 7.0.<ref name="scalar-types" /> PHP 7.0 also has type declarations for function return types, expressed by placing the type name after the list of parameters, preceded by a colon.<ref name="return-types" /> For example, the <code>getAdder</code> function from the earlier example could be annotated with types like so in PHP 7: |
|||
<source lang="php"> |
|||
<pre> |
|||
function |
function lock() |
||
{ |
|||
return function(int $y) use ($x) : int { |
|||
$file = fopen('file.txt', 'r+'); |
|||
return $x + $y; |
|||
}; |
|||
retry: |
|||
if (!flock($file, LOCK_EX | LOCK_NB)) |
|||
goto retry; |
|||
fwrite($file, 'Success!'); |
|||
fclose($file); |
|||
} |
} |
||
</source> |
|||
When <code>flock()</code> is called, PHP opens a file and tries to lock it. The target label <code>retry:</code> defines the point to which execution should return if <code>flock()</code> is unsuccessful and <code>goto retry;</code> is called. The <code>goto</code> statement is restricted and requires that the target label be in the same file and context. |
|||
$adder = getAdder(8); |
|||
echo $adder(2); // prints "10" |
|||
echo $adder(null); // throws an exception because an incorrect type was passed |
|||
$adder = getAdder([]); // would also throw an exception |
|||
</pre> |
|||
The <code>goto</code> statement has been supported since PHP 5.3. |
|||
By default, scalar type declarations follow weak typing principles. So, for example, if a parameter's type is <code>int</code>, PHP would allow not only integers, but also convertible numeric strings, floats or booleans to be passed to that function, and would convert them.<ref name="scalar-types" /> However, PHP 7 has a "strict typing" mode which, when used, disallows such conversions for function calls and returns within a file.<ref name="scalar-types" /> |
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=== Objects === |
=== Objects === |
||
Basic [[object-oriented programming]] functionality was added in PHP 3 and improved in PHP 4.<ref name="about PHP"/> |
Basic [[object-oriented programming]] functionality was added in PHP 3 and improved in PHP 4.<ref name="about PHP"/> Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance.<ref name="php 5 objects" /> In previous versions of PHP, objects were handled like [[value type]]s.<ref name="php 5 objects">{{cite web|accessdate=2008-03-16|url=http://mjtsai.com/blog/2004/07/15/php-5-object-references/|title=PHP 5 Object References |publisher=mjtsai}}</ref> The drawback of this method was that the whole object was copied when a variable was assigned or passed as a parameter to a method. In the new approach, objects are referenced by [[handle (computing)|handle]], and not by value. |
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PHP 5 introduced private and protected [[member variable]]s and methods, along with [[abstract type|abstract classes]], [[final type|final classes]], [[abstract method]]s, and [[final method]]s. It also introduced a standard way of declaring [[constructor (computer science)|constructors]] and [[destructor (computer science)|destructors]], similar to that of other object-oriented languages such as [[C++]], and a standard [[exception handling]] model. Furthermore, PHP 5 added [[interface (computing)|interface]]s and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. [[object (computer science)|Objects]] implementing ArrayAccess can be used with [[array data type|array]] syntax and objects implementing [[Iterator]] or [[IteratorAggregate]] can be used with the <code>foreach</code> [[language construct]]. There is no [[virtual table]] feature in the engine, so [[static variable]]s are bound with a name instead of a reference at compile time.<ref name="zend engine 2">{{cite web|accessdate=2008-03-16|url=http://www.php.net/zend-engine-2.php|title=Classes and Objects (PHP 5) |publisher=The PHP Group}}</ref> |
PHP 5 introduced private and protected [[member variable]]s and methods, along with [[abstract type|abstract classes]], [[final type|final classes]], [[abstract method]]s, and [[final method]]s. It also introduced a standard way of declaring [[constructor (computer science)|constructors]] and [[destructor (computer science)|destructors]], similar to that of other object-oriented languages such as [[C++]], and a standard [[exception handling]] model. Furthermore, PHP 5 added [[interface (computing)|interface]]s and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. [[object (computer science)|Objects]] implementing ArrayAccess can be used with [[array data type|array]] syntax and objects implementing [[Iterator]] or [[IteratorAggregate]] can be used with the <code>foreach</code> [[language construct]]. There is no [[virtual table]] feature in the engine, so [[static variable]]s are bound with a name instead of a reference at compile time.<ref name="zend engine 2">{{cite web|accessdate=2008-03-16|url=http://www.php.net/zend-engine-2.php|title=Classes and Objects (PHP 5) |publisher=The PHP Group}}</ref> |
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Line 394: | Line 376: | ||
The following is a basic example of [[object-oriented programming]] in PHP: |
The following is a basic example of [[object-oriented programming]] in PHP: |
||
<source lang="php"> |
|||
<pre> |
|||
class Person |
class Person |
||
{ |
{ |
||
Line 429: | Line 411: | ||
echo Person::staticGreet('Jane', 'Doe'); // prints "Hello, my name is Jane Doe." |
echo Person::staticGreet('Jane', 'Doe'); // prints "Hello, my name is Jane Doe." |
||
</ |
</source> |
||
The [[visibility (computer science)|visibility]] of PHP properties and methods is defined using the [[keyword (computer programming)|keywords]] <code>public</code>, <code>private</code>, and <code>protected</code>. The default is public, if only [[variable (programming)|var]] is used; <code>var</code> is a synonym for <code>public</code>. Items declared <code>public</code> can be accessed everywhere. <code>protected</code> limits access to [[inherited class]]es (and to the class that defines the item). <code>private</code> limits visibility only to the class that defines the item.<ref>{{cite web|url=http://theserverpages.com/php/manual/en/language.oop5.visibility.php |title= Visibility |
The [[visibility (computer science)|visibility]] of PHP properties and methods is defined using the [[keyword (computer programming)|keywords]] <code>public</code>, <code>private</code>, and <code>protected</code>. The default is public, if only [[variable (programming)|var]] is used; <code>var</code> is a synonym for <code>public</code>. Items declared <code>public</code> can be accessed everywhere. <code>protected</code> limits access to [[inherited class]]es (and to the class that defines the item). <code>private</code> limits visibility only to the class that defines the item.<ref>{{cite web|url=http://theserverpages.com/php/manual/en/language.oop5.visibility.php |title= Visibility | work = PHP Manual |publisher=Theserverpages.com |date=2005-05-19 |accessdate=2010-08-26}}</ref> Objects of the same type have access to each other's private and protected members even though they are not the same instance. PHP's member visibility features have sometimes been described as "highly useful."<ref>{{cite web |url=http://www.devshed.com/c/a/PHP/More-on-Private-Methods-with-PHP-5-Member-Visibility/ |title=More on Private Methods with PHP 5 Member Visibility |first= Alejandro |last=Gervasio |publisher=devshed.com |accessdate=24 November 2010}}</ref> However, they have also sometimes been described as "at best irrelevant and at worst positively harmful."<ref>{{cite web|url=http://aperiplus.sourceforge.net/visibility.php |title=Visibility in PHP: Public, Private and Protected |publisher=Aperiplus.sourceforge.net |accessdate=2010-08-26}}</ref> |
||
== Implementations == |
== Implementations == |
||
The original, only complete and most widely used PHP implementation is powered by the [[Zend Engine]] and known simply as PHP. To disambiguate it from other implementations, it is sometimes unofficially referred to as "Zend PHP". The Zend Engine [[Compiler|compiles]] PHP [[source code]] on-the-fly into an internal format that it can execute, thus it works as an [[Interpreter (computing)|interpreter]].<ref>{{cite web|accessdate=2009-11-04|url=http://www.linux-tutorial.info/modules.php?name=Howto&pagename=Unix-and-Internet-Fundamentals-HOWTO/languages.html|title=How do computer languages work?}}</ref><ref>{{harv|Gilmore|2006|p=43}}</ref> It is also the "reference implementation" of PHP, as PHP has no formal specification, and so the semantics of Zend PHP define the semantics of PHP itself. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility. |
The original, only complete and most widely used PHP implementation is powered by the [[Zend Engine]] and known simply as PHP. To disambiguate it from other implementations, it is sometimes unofficially referred to as "Zend PHP". The Zend Engine [[Compiler|compiles]] PHP [[source code]] on-the-fly into an internal format that it can execute, thus it works as an [[Interpreter (computing)|interpreter]].<ref>{{cite web|accessdate=2009-11-04|url=http://www.linux-tutorial.info/modules.php?name=Howto&pagename=Unix-and-Internet-Fundamentals-HOWTO/languages.html|title=How do computer languages work?}}</ref><ref>{{harv|Gilmore|2006|p=43}}</ref> It is also the "reference implementation" of PHP, as PHP has no formal specification, and so the semantics of Zend PHP define the semantics of PHP itself. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility. |
||
PHP's single-request-per-script-execution model, and the fact the Zend Engine is an interpreter, |
PHP's single-request-per-script-execution model, and the fact the Zend Engine is an interpreter, led to inefficiency. As a result, various products have been developed to help improve PHP performance. In order to speed up execution time and not have to compile the PHP source code every time the web page is accessed, PHP scripts can also be deployed in the PHP engine's internal format by using an [[opcode]] cache, which works by [[Cache (computing)|caching]] the compiled form of a PHP script (opcodes) in [[shared memory]] to avoid the overhead of [[parsing]] and [[compiling]] the code every time the script runs. An opcode cache, [[Zend Opcache]], is built into PHP since version 5.5.<ref>{{cite web |
||
| title = [VOTE] Integrating Zend Optimizer+ into the PHP distribution |
| title = [VOTE] Integrating Zend Optimizer+ into the PHP distribution |
||
| url = http://news.php.net/php.internals/66531 |
| url = http://news.php.net/php.internals/66531 |
||
| accessdate = 2013-03-08 |
| accessdate = 2013-03-08 |
||
| |
| publisher = PHP.net |
||
}}</ref> Another example of a widely used opcode cache is the [[Alternative PHP Cache]] (APC), which is available as a [[PHP Extension Community Library|PECL]] extension.<ref>{{cite web |
}}</ref> Another example of a widely used opcode cache is the [[Alternative PHP Cache]] (APC), which is available as a [[PHP Extension Community Library|PECL]] extension.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/book.apc.php |
| url = http://www.php.net/manual/en/book.apc.php |
||
| title = Alternative PHP Cache |
| title = Alternative PHP Cache |
||
| accessdate = 2013-09-21 |
| accessdate = 2013-09-21 |
||
| |
| publisher = PHP.net |
||
}}</ref> |
}}</ref> |
||
While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these are [[compiler]]s or support [[JIT compilation]], and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility. Alternative implementations include the following: |
While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these are [[compiler]]s or support [[JIT compilation]], and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility. Alternative implementations include the following: |
||
* [[HipHop Virtual Machine]] (HHVM){{snd}} developed at Facebook and available as open source, it converts PHP code into a high-level bytecode (commonly known as an [[intermediate language]]), which is then translated into x86-64 machine code dynamically at runtime by a [[Just-in-time compiler|just-in-time]] (JIT) compiler, resulting in up to 6× performance improvements.<ref>{{cite web|url=http://www.hhvm.com/blog/2813/we-are-the-98-5-and-the-16 |title=We are the 98.5% (and the 16%) « HipHop Virtual Machine | |
* [[HipHop Virtual Machine]] (HHVM){{snd}} developed at Facebook and available as open source, it converts PHP code into a high-level bytecode (commonly known as an [[intermediate language]]), which is then translated into x86-64 machine code dynamically at runtime by a [[Just-in-time compiler|just-in-time]] (JIT) compiler, resulting in up to 6× performance improvements.<ref>{{cite web|url=http://www.hhvm.com/blog/2813/we-are-the-98-5-and-the-16 |title=We are the 98.5% (and the 16%) « HipHop Virtual Machine |publisher=Hhvm.com |date=December 2013 |accessdate=2014-02-23}}</ref> |
||
* [[Parrot virtual machine|Parrot]]{{snd}} a virtual machine designed to run dynamic languages efficiently; Pipp transforms the PHP source code into the [[Parrot intermediate representation]], which is then translated into the Parrot's bytecode and executed by the virtual machine. |
* [[Parrot virtual machine|Parrot]]{{snd}} a virtual machine designed to run dynamic languages efficiently; Pipp transforms the PHP source code into the [[Parrot intermediate representation]], which is then translated into the Parrot's bytecode and executed by the virtual machine. |
||
* [[Phalanger (compiler)|Phalanger]]{{snd}} compiles PHP into [[Common Intermediate Language]] (CIL) bytecode |
* [[Phalanger (compiler)|Phalanger]]{{snd}} compiles PHP into [[Common Intermediate Language]] (CIL) bytecode |
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}} |
}} |
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This restriction on use of |
This restriction on use of the name ''PHP'' makes it incompatible with the [[GNU General Public License]] (GPL).<ref>{{cite web | title = GPL-Incompatible, Free Software Licenses | url = https://www.gnu.org/licenses/license-list.html#GPLIncompatibleLicenses | work = Various Licenses and Comments about Them | publisher = Free Software Foundation|accessdate=2011-01-03}}</ref> |
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== {{Anchor|PDO|ZEPHIR}}Development and community == |
== {{Anchor|PDO|ZEPHIR}}Development and community == |
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PHP includes |
PHP includes [[list of PHP libraries|free and open source libraries]] with the core build. PHP is a fundamentally [[Internet]]-aware system with modules built in for accessing [[File Transfer Protocol]] (FTP) servers, many database servers, embedded SQL libraries such as embedded [[PostgreSQL]], [[MySQL]], [[Microsoft SQL Server]] and [[SQLite]], [[Lightweight Directory Access Protocol|LDAP]] servers, and others. Many functions familiar to C programmers such as those in the [[stdio.h|stdio]] family are available in the standard PHP build.<ref>{{cite web|accessdate=2008-02-25|url=http://www.php.net/quickref.php|title=PHP Function List |publisher=The PHP Group}}</ref> |
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PHP allows developers to write [[Software extension|extensions]] in [[C (programming language)|C]] to add functionality to the PHP language. PHP extensions can be compiled statically into PHP or loaded dynamically at runtime. Numerous extensions have been written to add support for the [[Windows API]], process management on [[Unix-like]] [[operating system]]s, multibyte strings ([[Unicode]]), [[cURL]], and several popular [[archive format|compression formats]]. Other PHP features made available through extensions include integration with [[Internet Relay Chat|IRC]], dynamic generation of images and [[Adobe Flash]] content, ''PHP Data Objects'' (PDO) as an abstraction layer used for accessing databases,<ref>{{cite web|url=http://www.php.net/manual/en/intro.pdo.php |title=Introduction - Manual | |
PHP allows developers to write [[Software extension|extensions]] in [[C (programming language)|C]] to add functionality to the PHP language. PHP extensions can be compiled statically into PHP or loaded dynamically at runtime. Numerous extensions have been written to add support for the [[Windows API]], process management on [[Unix-like]] [[operating system]]s, multibyte strings ([[Unicode]]), [[cURL]], and several popular [[archive format|compression formats]]. Other PHP features made available through extensions include integration with [[Internet Relay Chat|IRC]], dynamic generation of images and [[Adobe Flash]] content, ''PHP Data Objects'' (PDO) as an abstraction layer used for accessing databases,<ref>{{cite web|url=http://www.php.net/manual/en/intro.pdo.php |title=Introduction - Manual |publisher=PHP |date=2013-06-07 |accessdate=2013-06-13}}</ref><ref>[http://www.onlamp.com/pub/a/php/2004/08/05/dataobjects.html O'Reilly Networks - ONLamp]</ref><ref>[http://www-128.ibm.com/developerworks/db2/library/techarticle/dm-0612xia/ IBM DeveloperWorks]</ref><ref>{{cite web|url=http://www-128.ibm.com/developerworks/library/os-php-dbmistake/index.html |title=Five common PHP database problems |publisher=128.ibm.com |date=2006-08-01 |accessdate=2013-06-13}}</ref><ref>[http://www.redbooks.ibm.com/abstracts/sg247218.html IBM Redbooks]</ref><ref>[http://www.phparch.com/issue.php?mid=65 php|architect]</ref><ref>[http://www.infoworld.com/article/05/10/19/HNphpshow_1.html Info]</ref> and even [[speech synthesis]]. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions.<ref>[http://lxr.php.net/xref/PHP_5_4/ext/standard/ Cross Reference: /PHP_5_4/ext/standard/]</ref> The [[PHP Extension Community Library]] (PECL) project is a repository for extensions to the PHP language.<ref>{{cite web|accessdate=2008-02-25|url=http://www.devnewz.com/090902b.html|title=Developing Custom PHP Extensions |publisher=devnewz|date=2002-09-09 |archiveurl = http://web.archive.org/web/20080218045752/http://www.devnewz.com/090902b.html |archivedate = 2008-02-18}}</ref> |
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Some other projects, such as ''Zephir'', provide the ability for PHP extensions to be created in a high-level language and compiled into native PHP extensions. Such an approach, instead of writing PHP extensions directly in C, simplifies the development of extensions and reduces the time required for programming and testing.<ref>{{cite web |
Some other projects, such as ''Zephir'', provide the ability for PHP extensions to be created in a high-level language and compiled into native PHP extensions. Such an approach, instead of writing PHP extensions directly in C, simplifies the development of extensions and reduces the time required for programming and testing.<ref>{{cite web |
||
| url = http:// |
| url = http://zephir-lang.com/motivation.html |
||
| title = Why Zephir? |
| title = Why Zephir? |
||
| date = |
| date = 2014-04-28 | accessdate = 2014-07-15 |
||
| website = zephir-lang.com |
| website = zephir-lang.com |
||
}}</ref> |
}}</ref> |
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The PHP Group consists of ten people ({{as of|2015|lc=on}}): [[Thies C. Arntzen]], [[Stig Bakken]], [[Shane Caraveo]], [[Andi Gutmans]], [[Rasmus Lerdorf]], [[Sam Ruby]], [[Sascha Schumann]], [[Zeev Suraski]], [[Jim Winstead]], [[Andrei Zmievski]].<ref>{{cite web|title=PHP Credits|url=http://php.net/credits.php|website=php.net|accessdate=2015-07-29}}</ref> |
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[[Zend Technologies]] provides a [[Zend Certified Engineer|certification]] exam for programmers to become certified PHP developers. |
[[Zend Technologies]] provides a [[Zend Certified Engineer|certification]] exam for programmers to become certified PHP developers. |
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| title = General Installation Considerations |
| title = General Installation Considerations |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
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| |
| publisher = PHP.net |
||
}}</ref> |
}}</ref> |
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| title = News Archive: PHP 5.3.3 Released! |
| title = News Archive: PHP 5.3.3 Released! |
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| date = 2010-07-22 |
| date = 2010-07-22 |
||
| |
| publisher = PHP.net}}</ref> When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/install.fpm.php |
| url = http://www.php.net/manual/en/install.fpm.php |
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| title = FastCGI Process Manager (FPM) |
| title = FastCGI Process Manager (FPM) |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> |
}}</ref> |
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| title = Command line usage: Introduction |
| title = Command line usage: Introduction |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> The main focus of this SAPI is developing [[command line interface|shell]] applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviors.<ref>{{cite web |
}}</ref> The main focus of this SAPI is developing [[command line interface|shell]] applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviors.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/features.commandline.differences.php |
| url = http://www.php.net/manual/en/features.commandline.differences.php |
||
| title = Command line usage: Differences to other SAPIs |
| title = Command line usage: Differences to other SAPIs |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> |
}}</ref> |
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| title = Installing PHP-GTK 2 |
| title = Installing PHP-GTK 2 |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> |
}}</ref> |
||
When PHP is installed and used in [[Cloud computing|cloud]] environments, [[software development kit]]s (SDKs) are provided for using cloud-specific features. For example: |
When PHP is installed and used in [[Cloud computing|cloud]] environments, [[software development kit]]s (SDKs) are provided for using cloud-specific features. For example: |
||
* [[Amazon Web Services]] provides the AWS SDK for PHP<ref>{{cite web|url=http://aws.amazon.com/sdkforphp/ |title=AWS SDK for PHP | |
* [[Amazon Web Services]] provides the AWS SDK for PHP<ref>{{cite web|url=http://aws.amazon.com/sdkforphp/ |title=AWS SDK for PHP |publisher=Aws.amazon.com |accessdate=2014-03-06}}</ref> |
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* [[Windows Azure]] can be used with the Windows Azure SDK for PHP.<ref>{{cite web|url=http://www.interoperabilitybridges.com/projects/php-sdk-for-windows-azure.aspx |title=Windows Azure SDK for PHP - Interoperability Bridges and Labs Center | |
* [[Windows Azure]] can be used with the Windows Azure SDK for PHP.<ref>{{cite web|url=http://www.interoperabilitybridges.com/projects/php-sdk-for-windows-azure.aspx |title=Windows Azure SDK for PHP - Interoperability Bridges and Labs Center |publisher=Interoperabilitybridges.com |accessdate=2014-03-06}}</ref> |
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Numerous configuration options are supported, affecting both core PHP features and extensions.<ref>{{cite web |
Numerous configuration options are supported, affecting both core PHP features and extensions.<ref>{{cite web |
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Line 526: | Line 506: | ||
| title = Runtime configuration: Table of contents |
| title = Runtime configuration: Table of contents |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
||
| url = http://www.php.net/manual/en/ini.list.php |
| url = http://www.php.net/manual/en/ini.list.php |
||
| title = php.ini directives: List of php.ini directives |
| title = php.ini directives: List of php.ini directives |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> Configuration file <code>php.ini</code> is searched for in different locations, depending on the way PHP is used.<ref>{{cite web |
}}</ref> Configuration file <code>php.ini</code> is searched for in different locations, depending on the way PHP is used.<ref>{{cite web |
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| url = http://www.php.net/manual/en/configuration.file.php |
| url = http://www.php.net/manual/en/configuration.file.php |
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PHP is a general-purpose scripting language that is especially suited to [[server-side scripting|server-side]] [[web development]], in which case PHP generally runs on a [[web server]]. Any PHP code in a requested file is [[execution (computing)|executed]] by the PHP runtime, usually to create [[dynamic web page]] content or dynamic images used on websites or elsewhere.<ref>{{cite web|url=http://php.net/manual/en/book.image.php |title=PHP Manual Image Processing and GD; |publisher= php.net |accessdate=2011-04-09}}</ref> It can also be used for [[command-line]] scripting and [[client-side]] [[graphical user interface]] (GUI) applications. PHP can be deployed on most web servers, many [[operating system]]s and [[computing platform|platforms]], and can be used with many [[relational database management system]]s (RDBMS). Most [[web hosting]] providers support PHP for use by their clients. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use.<ref name="foundations">{{cite web|accessdate=2008-02-25|url=http://www.onlamp.com/pub/a/php/2001/05/03/php_foundations.html|title=Embedding PHP in HTML |publisher=O'Reilly|date=2001-05-03}}</ref> |
PHP is a general-purpose scripting language that is especially suited to [[server-side scripting|server-side]] [[web development]], in which case PHP generally runs on a [[web server]]. Any PHP code in a requested file is [[execution (computing)|executed]] by the PHP runtime, usually to create [[dynamic web page]] content or dynamic images used on websites or elsewhere.<ref>{{cite web|url=http://php.net/manual/en/book.image.php |title=PHP Manual Image Processing and GD; |publisher= php.net |accessdate=2011-04-09}}</ref> It can also be used for [[command-line]] scripting and [[client-side]] [[graphical user interface]] (GUI) applications. PHP can be deployed on most web servers, many [[operating system]]s and [[computing platform|platforms]], and can be used with many [[relational database management system]]s (RDBMS). Most [[web hosting]] providers support PHP for use by their clients. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use.<ref name="foundations">{{cite web|accessdate=2008-02-25|url=http://www.onlamp.com/pub/a/php/2001/05/03/php_foundations.html|title=Embedding PHP in HTML |publisher=O'Reilly|date=2001-05-03}}</ref> |
||
PHP acts primarily as a [[filter (software)|filter]],<ref>{{Wayback|url= |
PHP acts primarily as a [[filter (software)|filter]],<ref>{{Wayback|url=http://web.archive.org/web/20080611231433/http://gtk.php.net/manual1/it/html/intro.whatis.php.whatdoes.html|title=|date=20080611231433}}{{Failed verification|date=April 2010}}</ref> taking input from a file or stream containing text and/or PHP instructions and outputting another stream of data. Most commonly the output will be HTML, although it could be [[JSON]], [[XML]] or [[binary data]] such as image or audio formats. Since PHP 4, the PHP [[parser]] [[compiler|compiles]] input to produce [[bytecode]] for processing by the [[Zend Engine]], giving improved performance over its [[interpreter (computing)|interpreter]] predecessor.<ref>{{cite web|accessdate=2008-02-25|url=http://cs.ua.edu/457/Notes/PHP%20and%20MySQL.ppt|title=PHP and MySQL |publisher=[[University of Alabama]] |archiveurl = http://web.archive.org/web/20080228003031/http://cs.ua.edu/457/Notes/PHP+and+MySQL.ppt <!-- Bot retrieved archive --> |archivedate = 2008-02-28}}</ref> |
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Originally designed to create dynamic [[web page]]s, PHP now focuses mainly on [[server-side scripting]],<ref>{{cite web|url=http://webmaster.iu.edu/PHPlanguage/index.shtml|title=PHP Server-Side Scripting Language|publisher=[[Indiana University]]|accessdate=2008-02-25|date=2007-04-04}}</ref> and it is similar to other server-side scripting languages that provide dynamic content from a web server to a [[client (computing)|client]], such as [[Microsoft]]'s [[ASP.NET]], [[Sun Microsystems]]' [[JavaServer Pages]],<ref>{{cite web|url=http://java.sun.com/products/jsp/jspservlet.html|title=JavaServer Pages Technology — JavaServer Pages Comparing Methods for Server-Side Dynamic Content White Paper|publisher=Sun Microsystems|accessdate=2008-02-25}}</ref> and <tt>[[mod_perl]]</tt><!-- do not remove the underscore from mod_perl: it is part of the name -->. PHP has also attracted the development of many [[software framework]]s that provide building blocks and a design structure to promote [[rapid application development]] (RAD). Some of these include [[PRADO (framework)|PRADO]], [[CakePHP]], [[Symfony]], [[CodeIgniter]], [[Laravel]], [[Yii Framework]], |
Originally designed to create dynamic [[web page]]s, PHP now focuses mainly on [[server-side scripting]],<ref>{{cite web|url=http://webmaster.iu.edu/PHPlanguage/index.shtml|title=PHP Server-Side Scripting Language|publisher=[[Indiana University]]|accessdate=2008-02-25|date=2007-04-04}}</ref> and it is similar to other server-side scripting languages that provide dynamic content from a web server to a [[client (computing)|client]], such as [[Microsoft]]'s [[ASP.NET]], [[Sun Microsystems]]' [[JavaServer Pages]],<ref>{{cite web|url=http://java.sun.com/products/jsp/jspservlet.html|title=JavaServer Pages Technology — JavaServer Pages Comparing Methods for Server-Side Dynamic Content White Paper|publisher=Sun Microsystems|accessdate=2008-02-25}}</ref> and <tt>[[mod_perl]]</tt><!-- do not remove the underscore from mod_perl: it is part of the name -->. PHP has also attracted the development of many [[software framework]]s that provide building blocks and a design structure to promote [[rapid application development]] (RAD). Some of these include [[PRADO (framework)|PRADO]], [[CakePHP]], [[Symfony]], [[CodeIgniter]], [[Laravel (framework)|Laravel]], [[Yii Framework]], and [[Zend Framework]], offering features similar to other [[list of web application frameworks|web application frameworks]]. |
||
The [[ |
The [[LAMP architecture]] has become popular in the web industry as a way of deploying web applications.<ref>{{cite web|url=http://www.ibm.com/developerworks/library/os-5waystunelamp/index.html|title=Five simple ways to tune your LAMP application}}</ref> PHP is commonly used as the ''P'' in this bundle alongside [[Linux]], [[Apache HTTP Server|Apache]] and [[MySQL]], although the ''P'' may also refer to [[Python (programming language)|Python]], [[Perl]], or some mix of the three. Similar packages, [[WAMP (software bundle)|WAMP]] and [[MAMP]], are also available for [[Microsoft Windows|Windows]] and [[OS X]], with the first letter standing for the respective operating system. Although both PHP and Apache are provided as part of the Mac OS X base install, users of these packages seek a simpler installation mechanism that can be more easily kept up to date. |
||
{{As of|2007|04}}, over 20 million Internet domains had web services hosted on servers with PHP installed and <tt>mod_php</tt> was recorded as the most popular [[Apache HTTP Server]] module.<ref name="usage">{{cite web |
{{As of|2007|04}}, over 20 million Internet domains had web services hosted on servers with PHP installed and <tt>mod_php</tt> was recorded as the most popular [[Apache HTTP Server]] module.<ref name="usage">{{cite web |
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|publisher=SecuritySpace |
|publisher=SecuritySpace |
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|accessdate=2008-02-24 |
|accessdate=2008-02-24 |
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|date=2007-04-01}}</ref> {{As of|2010|10}}, PHP was used as the server-side programming language on 75% of all websites whose server-side programming language was known<ref name="W3Techs usage |
|date=2007-04-01}}</ref> {{As of|2010|10}}, PHP was used as the server-side programming language on 75% of all websites whose server-side programming language was known<ref name="W3Techs usage statistics">{{cite web |
||
| title=Usage of server-side programming languages for websites |
| title=Usage of server-side programming languages for websites |
||
| url=http://w3techs.com/technologies/overview/programming_language/all |
| url=http://w3techs.com/technologies/overview/programming_language/all |
||
|publisher=W3Techs |
|publisher=W3Techs |
||
|accessdate=2010-10-29 |
|accessdate=2010-10-29 |
||
|date=2010-10-29}}</ref> ({{As of|2014|02|lc=yes}}, the percentage had reached 82%<ref name="W3Techs usage |
|date=2010-10-29}}</ref> ({{As of|2014|02|lc=yes}}, the percentage had reached 82%<ref name="W3Techs usage statistics">{{cite web |
||
| title=Usage of server-side programming languages for websites |
| title=Usage of server-side programming languages for websites |
||
| url=http://w3techs.com/technologies/overview/programming_language/all |
| url=http://w3techs.com/technologies/overview/programming_language/all |
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|publisher=W3Techs |
|publisher=W3Techs |
||
|accessdate=2014-03-19 |
|accessdate=2014-03-19 |
||
}}</ref>), and PHP was the most-used open source software within enterprises.<ref>{{cite web|url=http://news.cnet.com/8301-13505_3-10453213-16.html|title=PHP and Perl crashing the enterprise party}}</ref> [[Web content management system]]s written in PHP include [[MediaWiki]],<ref>{{cite web|url=http://www.mediawiki.org/w/index.php?title=Manual:Installation_requirements&oldid=299556#PHP |title=Manual:Installation requirements#PHP |publisher=MediaWiki |date=2010-01-25 |accessdate=2010-02-26|quote=PHP is the programming language in which MediaWiki is written [...]}}</ref> [[Joomla]], |
}}</ref>), and PHP was the most-used open source software within enterprises.<ref>{{cite web|url=http://news.cnet.com/8301-13505_3-10453213-16.html|title=PHP and Perl crashing the enterprise party}}</ref> [[Web content management system]]s written in PHP include [[MediaWiki]],<ref>{{cite web|url=http://www.mediawiki.org/w/index.php?title=Manual:Installation_requirements&oldid=299556#PHP |title=Manual:Installation requirements#PHP |publisher=MediaWiki |date=2010-01-25 |accessdate=2010-02-26|quote=PHP is the programming language in which MediaWiki is written [...]}}</ref> [[Joomla]], [[eZ Publish]], [[SilverStripe]],<ref>{{cite web|url=http://www.silverstripe.org/system-requirements/ |title=System requirements of SilverStripe|accessdate=2012-03-05|quote=SilverStripe requires PHP 5.2+}}</ref> [[WordPress]],<ref>{{cite web|url=http://wordpress.org/about/ |title=About WordPress|accessdate=2010-02-26|quote=WordPress was [...] built on PHP}}</ref> [[Drupal]],<ref>{{cite web|url=http://drupal.org/node/176052 |title=PHP and Drupal |publisher=Drupal.org |accessdate=2010-06-13}}</ref> [[Moodle]],<ref>{{cite web|url=http://docs.moodle.org/en/About_Moodle |title= About |publisher=Moodle.org |accessdate=2009-12-20}}</ref> the user-facing portion of [[Facebook]],<ref>{{cite web|url=http://blog.facebook.com/blog.php?post=2356432130 |title=PHP and Facebook | Facebook |publisher=Blog.facebook.com |accessdate=2009-07-29}}</ref> and [[Digg]].<ref>{{cite web|url=http://www.oreillynet.com/onlamp/blog/2006/04/digg_phps_scalability_and_perf.html |title=PHP and Digg |publisher=O'Reilly |accessdate=2010-06-13}}</ref> |
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For specific and more advanced usage scenarios, PHP offers a well defined and documented way for writing custom extensions in [[C (programming language)|C]] or [[C++]].<ref>{{cite web |
For specific and more advanced usage scenarios, PHP offers a well defined and documented way for writing custom extensions in [[C (programming language)|C]] or [[C++]].<ref>{{cite web |
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| title = PHP at the core: Extension structure |
| title = PHP at the core: Extension structure |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
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| |
| publisher = PHP.net |
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}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
||
| url = http://www.php.net/manual/en/internals2.counter.php |
| url = http://www.php.net/manual/en/internals2.counter.php |
||
| title = PHP at the core: The "counter" Extension |
| title = PHP at the core: The "counter" Extension - A Continuing Example |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
||
| url = http://devzone.zend.com/303/extension-writing-part-i-introduction-to-php-and-zend/ |
| url = http://devzone.zend.com/303/extension-writing-part-i-introduction-to-php-and-zend/ |
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}}</ref><ref>{{cite web |
}}</ref><ref>{{cite web |
||
| url = http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/ |
| url = http://devzone.zend.com/318/extension-writing-part-ii-parameters-arrays-and-zvals-continued/ |
||
| title = Extension Writing Part II: Parameters, Arrays, and ZVALs |
| title = Extension Writing Part II: Parameters, Arrays, and ZVALs [continued] |
||
| date = 2005-06-06 | accessdate = 2013-09-22 |
| date = 2005-06-06 | accessdate = 2013-09-22 |
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| publisher = [[Zend Technologies]] |
| publisher = [[Zend Technologies]] |
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| title = Bug Request #46919: Multi threading |
| title = Bug Request #46919: Multi threading |
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| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref> though using threads is made possible by the "pthreads" [[PHP Extension Community Library|PECL]] extension.<ref>{{cite web |
}}</ref> though using threads is made possible by the "pthreads" [[PHP Extension Community Library|PECL]] extension.<ref>{{cite web |
||
| url = http://www.php.net/manual/en/intro.pthreads.php |
| url = http://www.php.net/manual/en/intro.pthreads.php |
||
| title = pthreads: Introduction |
| title = pthreads: Introduction | work = PHP Manual |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| |
| publisher = PHP.net |
||
}}</ref><ref>{{cite web|url=http://pecl.php.net/package/pthreads |title=PECL :: Package :: pthreads | |
}}</ref><ref>{{cite web|url=http://pecl.php.net/package/pthreads |title=PECL :: Package :: pthreads |publisher=Pecl.php.net |accessdate=2014-02-09}}</ref> |
||
{{As of|2013|1}}, PHP was used in more than 240 million [[website]]s (39% of those sampled) and was installed on 2.1 million [[web server]]s.<ref>{{cite web | url=http://news.netcraft.com/archives/2013/01/31/php-just-grows-grows.html | title=PHP just grows & grows | date=2013-01-31 | accessdate=2013-04-01 | author=Ide, Andy}}</ref> |
|||
== {{Anchor|REGISTER-GLOBALS}}Security == |
== {{Anchor|REGISTER-GLOBALS}}Security == |
||
Line 650: | Line 628: | ||
| accessdate=2013-04-01 |
| accessdate=2013-04-01 |
||
}}</ref> Recognizing that programmers make mistakes, some languages include [[taint checking]] to automatically detect the lack of [[data validation|input validation]] which induces many issues. Such a feature is being developed for PHP,<ref>{{cite web |title=PHP Taint Mode RFC|url=http://wiki.php.net/rfc/taint}}</ref> but its inclusion into a release has been rejected several times in the past.<ref>{{cite web |
}}</ref> Recognizing that programmers make mistakes, some languages include [[taint checking]] to automatically detect the lack of [[data validation|input validation]] which induces many issues. Such a feature is being developed for PHP,<ref>{{cite web |title=PHP Taint Mode RFC|url=http://wiki.php.net/rfc/taint}}</ref> but its inclusion into a release has been rejected several times in the past.<ref>{{cite web |
||
| url=http:// |
| url=http://www.php.net/~derick/meeting-notes.html#sand-boxing-or-taint-mode |
||
| title=Developer Meeting Notes, Nov. 2005}}</ref><ref>{{cite web |
| title=Developer Meeting Notes, Nov. 2005}}</ref><ref>{{cite web |
||
| url=http://devzone.zend.com/article/2798-Zend-Weekly-Summaries-Issue-368#Heading1 |
| url=http://devzone.zend.com/article/2798-Zend-Weekly-Summaries-Issue-368#Heading1 |
||
Line 660: | Line 638: | ||
|date=2008-08-15}}</ref> |
|date=2008-08-15}}</ref> |
||
There are certain language features and configuration parameters (primarily the default values for such runtime settings) that make PHP |
There are certain language features and configuration parameters (primarily the default values for such runtime settings) that make PHP prone to security issues. Among these, <tt>[[magic quotes|magic_quotes_gpc]]</tt> and <tt>register_globals</tt><ref name="register-globals">{{cite web |
||
| url = http://php.net/manual/en/security.globals.php |
| url = http://php.net/manual/en/security.globals.php |
||
| title = Security: Using Register Globals | work = PHP Manual |
| title = Security: Using Register Globals | work = PHP Manual |
||
| accessdate = 2013-09-22 |
| accessdate = 2013-09-22 |
||
| publisher = PHP.net |
| publisher = PHP.net |
||
}}</ref> configuration directives are the best known; the latter made any URL parameters become PHP variables, opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script. Support for "[[magic quotes]]" and "register globals" has been deprecated as of PHP 5.3.0, and removed as of PHP 5.4.0.<ref name=" |
}}</ref> configuration directives are the best known; the latter made any URL parameters become PHP variables, opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script. Support for "[[magic quotes]]" and "register globals" has been deprecated as of PHP 5.3.0, and removed as of PHP 5.4.0.<ref name="register-globals" /><ref>{{cite web |
||
| url = http://www.php.net/manual/en/security.magicquotes.php |
| url = http://www.php.net/manual/en/security.magicquotes.php |
||
| title = Magic Quotes | work = PHP Manual |
| title = Magic Quotes | work = PHP Manual |
||
Line 709: | Line 687: | ||
}}</ref> |
}}</ref> |
||
Also, implied [[type conversion]]s that result in incompatible values being treated as identical against the programmer's intent can lead to security issues. For example, the result of |
Also, implied [[type conversion]]s that result in incompatible values being treated as identical against the programmer's intent can lead to security issues. For example, the result of <tt>0e1234 == 0</tt> comparison will be <tt>true</tt> because the first compared value will be treated as [[scientific notation]] of a number ({{val|0|e=1234}}) with value of zero. This feature resulted in authentication vulnerabilities in [[Simple Machines Forum]],<ref>{{cite web|url=http://raz0r.name/vulnerabilities/simple-machines-forum/|title= Simple Machines Forum <= 2.0.3 Admin Password Reset|author=Raz0r}}</ref> [[Typo3]]<ref>{{cite web|url=http://blog.nibblesec.org/2010/12/typo3-sa-2010-020-typo3-sa-2010-022.html|title=TYPO3-SA-2010-020, TYPO3-SA-2010-022 EXPLAINED|author=Nibble Security}}</ref> and [[phpBB]]<ref>{{cite web|url=http://ahack.ru/articles/cryptographic-security-and-php-applications.htm|title=Криптостойкость и небезопасное сравнение|author=Ahack.ru}}</ref> when [[MD5]] [[password hashing|password hashes]] were compared. Instead, identity operator (<tt>===</tt>) should be used; <tt>0e1234 === 0</tt> results in <tt>false</tt>.<ref>{{cite web|url=http://www.php.net/manual/en/language.operators.comparison.php |title=Comparison operators |publisher=PHP.net}}</ref> |
||
In a 2013 analysis of over 170,000 [[website defacement]]s, published by [[Zone-H]], the most frequently (53%) used technique was exploitation of [[file inclusion vulnerability]], mostly related to insecure usage of the PHP functions ''include'', ''require'', and ''allow_url_fopen''.<ref>{{cite web | url=https://ipsec.pl/web-application-security/most-common-attacks-web-applications.html | title=Most common attacks on web applications | publisher=IPSec.pl | date=2013 | accessdate=2015-04-15 | author=Pawel Krawczyk}}</ref><ref>{{cite web | url=https://ipsec.pl/application-security/2013/so-what-are-most-critical-application-flaws-new-owasp-top-10.html | title=So what are the "most critical" application flaws? On new OWASP Top 10 | publisher=IPSec.pl | date=2013 | accessdate=2015-04-15 | author=Pawel Krawczyk}}</ref> |
|||
== See also == |
== See also == |
||
Line 734: | Line 710: | ||
== References == |
== References == |
||
{{Reflist|30em}} |
{{Reflist|30em}} |
||
==Further reading== |
|||
* {{cite journal |quote=What’s the Absolute Minimum I Must Know About PHP? |url= http://www.bloomberg.com/graphics/2015-paul-ford-what-is-code/ |title=What is Code? |author=Paul Ford |date=June 11, 2015 |journal=[[Bloomberg Businessweek]] }} |
|||
== External links == |
== External links == |
||
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{{Spoken Wikipedia|En-PHP.ogg|2011-11-23}} |
{{Spoken Wikipedia|En-PHP.ogg|2011-11-23}} |
||
* {{Official website}} |
* {{Official website|php.net}} |
||
* {{dmoz|Computers/Programming/Languages/PHP}} |
* {{dmoz|Computers/Programming/Languages/PHP}} |
||
* [http://www.php.net/manual PHP Reference Manual] |
* [http://www.php.net/manual PHP Reference Manual] |
||
* |
* [https://github.com/php/php-src PHP source code repository @ Github] |
||
{{PHP}} |
{{PHP}} |
||
{{Web interfaces}} |
{{Web interfaces}} |
||
{{FOSS}} |
{{FOSS}} |
||
{{Authority control}} |
|||
[[Category:Free compilers and interpreters]] |
[[Category:Free compilers and interpreters]] |
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[[Category:Object-oriented programming languages]] |
[[Category:Object-oriented programming languages]] |
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[[Category:Text-oriented programming languages]] |
[[Category:Text-oriented programming languages]] |
||
[[Category:PHP]] |
[[Category:PHP programming language]] |
||
[[Category:PHP software]] |
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[[Category:Scripting languages]] |
[[Category:Scripting languages]] |
||
[[Category:Dynamically typed programming languages]] |
[[Category:Dynamically typed programming languages]] |
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[[Category:Programming languages created in 1995]] |
[[Category:Programming languages created in 1995]] |
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[[Category:Class-based programming languages]] |
[[Category:Class-based programming languages]] |
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[[Category:Software using the PHP license]] |
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[[Category:Articles with example code]] |
Revision as of 01:03, 18 January 2016
![]() | |
Paradigm | imperative, functional, object-oriented, procedural, reflective |
---|---|
Designed by | Rasmus Lerdorf |
Developer | The PHP Group |
First appeared | 1995[1] |
Stable release | 5.5.15[2]
/ July 24, 2014 |
Preview release | 5.6.0RC3[3]
/ July 31, 2014 |
Typing discipline | Dynamic, weak |
Implementation language | C |
OS | Cross-platform |
License | PHP License (most of Zend engine under Zend Engine License) |
Filename extensions | .php, .phtml, .php4, .php3, .php5, .phps |
Website | php |
Major implementations | |
Zend Engine, HHVM, Phalanger, Quercus, Project Zero, Parrot | |
Influenced by | |
Perl, C, C++, Java, Tcl[1] | |
Influenced | |
Hack | |
|
PHP is a server-side scripting language designed for web development but also used as a general-purpose programming language. As of January 2013[update], PHP was installed on more than 240 million websites (39% of those sampled) and 2.1 million web servers.[4] Originally created by Rasmus Lerdorf in 1994,[5] the reference implementation of PHP (powered by the Zend Engine) is now produced by The PHP Group.[6] While PHP originally stood for Personal Home Page,[5] it now stands for PHP: Hypertext Preprocessor, which is a recursive acronym.[7]
PHP code can be simply mixed with HTML code, or it can be used in combination with various templating engines and web frameworks. PHP code is usually processed by a PHP interpreter, which is usually implemented as a web server's native module or a Common Gateway Interface (CGI) executable. After the PHP code is interpreted and executed, the web server sends resulting output to its client, usually in form of a part of the generated web page – for example, PHP code can generate a web page's HTML code, an image, or some other data. PHP has also evolved to include a command-line interface (CLI) capability and can be used in standalone graphical applications.[8]
The canonical PHP interpreter, powered by the Zend Engine, is free software released under the PHP License. PHP has been widely ported and can be deployed on most web servers on almost every operating system and platform, free of charge.[9]
Despite its popularity, no written specification or standard exists for the PHP language; instead, the canonical PHP interpreter serves as a de facto standard. However, work on creating a formal specification has started in 2014.[10]
History
PHP development began in 1994 when the developer Rasmus Lerdorf wrote a series of Common Gateway Interface (CGI) Perl scripts, which he used to maintain his personal homepage. The tools performed tasks such as displaying his résumé and recording his web traffic.[6][11][12] He rewrote these scripts in C for performance reasons, extending them to add the ability to work with web forms and to communicate with databases, and called this implementation "Personal Home Page/Forms Interpreter" or PHP/FI.
PHP/FI could be used to build simple, dynamic web applications. Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" publicly to accelerate bug location and improve the code, on the Usenet discussion group comp.infosystems.www.authoring.cgi on June 8, 1995.[13][14] This release already had the basic functionality that PHP has as of 2013[update]. This included Perl-like variables, form handling, and the ability to embed HTML. The syntax resembled that of Perl but was simpler, more limited and less consistent.[6]
Early PHP was not intended to be a new programming language, and grew organically, with Lerdorf noting in retrospect: "I don’t know how to stop it, there was never any intent to write a programming language […] I have absolutely no idea how to write a programming language, I just kept adding the next logical step on the way."[15] A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997.
One criticism of PHP is that it was not originally designed, but instead it was developed organically;[15] among other things, this has led to inconsistent naming of functions and inconsistent ordering of their parameters.[16] In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping",[17] while in some very early versions of PHP the length of the function names was used internally as a hash function, so names were chosen to improve the distribution of hash values.[18]
Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive acronym PHP: Hypertext Preprocessor.[6] Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend Engine in 1999.[19] They also founded Zend Technologies in Ramat Gan, Israel.[6]
On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released.[6] As of August 2008 this branch reached version 4.4.9. PHP 4 is no longer under development nor will any security updates be released.[20][21]
On July 13, 2004, PHP 5 was released, powered by the new Zend Engine II.[6] PHP 5 included new features such as improved support for object-oriented programming, the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements.[22] In 2008 PHP 5 became the only stable version under development. Late static binding had been missing from PHP and was added in version 5.3.[23][24]
Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative,[25] provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.[26][27]
PHP interpreters are available on most existing 32-bit and 64-bit operating systems, either by building them from the PHP source code, or by using pre-built binaries.[28] For the PHP versions 5.3 and 5.4, the only available Microsoft Windows binary distributions were 32-bit x86 builds,[29][30] requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit x86-64 builds available for Microsoft Windows.[31]
PHP 6 and Unicode
PHP received mixed reviews due to lacking native Unicode support at the core language level.[32][33] In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the International Components for Unicode (ICU) library, and representing text strings as UTF-16 internally.[34] Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.[35]
However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project.[36] As a result, a PHP 5.3 release was created in 2009, with many non-Unicode features back-ported from PHP 6, notably namespaces. In March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared containing most remaining non-Unicode features from PHP 6, such as traits and closure re-binding.[37] Initial hopes were that a new plan would be formed for Unicode integration, but as of 2014 none has been adopted.
PHP 7
There was some dispute as to whether the next major version of PHP was to be called PHP 6 or PHP 7. While the PHP 6 unicode experiment had never been released, a number of articles and book titles referenced the old PHP 6 name, which might have caused confusion if a new release were to reuse the PHP 6 name.[38] After a vote, the name PHP 7 was chosen.[39]
Since 20 January 2014, work has been underway on an experimental PHP branch named PHPNG (PHP Next Generation), aimed at optimizing PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility. As of 14 July 2014[update], the main benchmark suite for the PHPNG project, which WordPress is used for, shows an almost 100% increase in performance.[40] PHPNG is intended by its authors to be the foundation of PHP 7.[41]
PHP 7 will contain an improved variable syntax which is internally consistent and complete, what is a long-standing issue in PHP. This will allow use of ->, [], (), {}, and :: operators with arbitrary meaningful left-hand-side expressions. The current implementation of this change has been made on top of the PHPNG branch.[42]
Release history
Color | Meaning | Development |
---|---|---|
Red | Old release | No development |
Yellow | Stable release | Security fixes |
Green | Stable release | Bug and security fixes |
Blue | Future release | New features |
Version | Release date | Supported until[43] | Notes |
---|---|---|---|
1.0 | 8 June 1995 | Officially called "Personal Home Page Tools (PHP Tools)". This is the first use of the name "PHP".[6] | |
2.0 | 1 November 1997 | Officially called "PHP/FI 2.0". This is the first release that could actually be characterised as PHP, being a standalone language with many features that have endured to the present day. | |
3.0 | 6 June 1998 | 20 October 2000 | Development moves from one person to multiple developers. Zeev Suraski and Andi Gutmans rewrite the base for this version.[6] |
4.0 | 22 May 2000 | 23 January 2001 | Added more advanced two-stage parse/execute tag-parsing system called the Zend engine.[44] |
4.1 | 10 December 2001 | 12 March 2002 | Introduced 'superglobals' ($_GET , $_POST , $_SESSION , etc.)[44]
|
4.2 | 22 April 2002 | 6 September 2002 | Disabled register_globals by default. Data received over the network is not inserted directly into the global namespace anymore, closing possible security holes in applications.[44]
|
4.3 | 27 December 2002 | 31 March 2005 | Introduced the command-line interface (CLI), to supplement the CGI.[44][45] |
4.4 | 11 July 2005 | 7 August 2008 | Fixed a memory corruption bug, which required breaking binary compatibility with extensions compiled against PHP version 4.3.x.[46] |
5.0 | 13 July 2004 | 5 September 2005 | Zend Engine II with a new object model.[47] |
5.1 | 24 November 2005 | 24 August 2006 | Performance improvements with introduction of compiler variables in re-engineered PHP Engine.[47] Added PHP Data Objects (PDO) as a consistent interface for accessing databases.[48] |
5.2 | 2 November 2006 | 6 January 2011 | Enabled the filter extension by default. Native JSON support.[47] |
5.3 | 30 June 2009 | 14 August 2014[49] | Namespace support; late static bindings, Jump label (limited goto), Native closures, Native PHP archives (phar), garbage collection for circular references, improved Windows support, sqlite3, mysqlnd as a replacement for libmysql as underlying library for the extensions that work with MySQL, fileinfo as a replacement for mime_magic for better MIME support, the Internationalization extension, and deprecation of ereg extension. |
5.4 | 1 March 2012 | 1 March 2015[50] | Trait support, short array syntax support. Removed items: register_globals , safe_mode , allow_call_time_pass_reference , session_register() , session_unregister() and session_is_registered() . Built-in web server.[51] Several improvements to existing features, performance and reduced memory requirements.
|
5.5 | 20 June 2013 | 20 June 2016[50] | Support for generators, finally blocks for exceptions handling, OpCache (based on Zend Optimizer+) bundled in official distribution.[52]
|
5.6 | No date set | 3 years after release[50] | Constant scalar expressions, variadic functions, argument unpacking, new exponentiation operator, extensions of the use statement for functions and constants, new phpdbg debugger as a SAPI module, and other smaller improvements.[53] |
Beginning on June 28, 2011, the PHP Group began following a timeline for when new versions of PHP will be released.[50] Under this timeline, at least one release should occur every month. Once per year, a minor release should occur which can include new features. Every minor release should at least have 2 years of security and bug fixes, followed by at least 1 year of only security fixes, for a total of a 3 year release process for every minor release. No new features (unless small and self-contained) will be introduced into a minor release during the 3-year release process.
Mascot
The mascot of the PHP project is the elePHPant, a blue (sometimes differently colored when in plush toy form) elephant with the PHP logo on its side.[citation needed]
-
The ElePHPant, PHP mascot
-
A plush toy elePHPant
Syntax
The following Hello world program is written in PHP code embedded in an HTML document:
<!DOCTYPE html>
<html>
<head>
<title>PHP Test</title>
</head>
<body>
<?php echo '<p>Hello World</p>'; ?>
</body>
</html>
However, as PHP does not need to be embedded in HTML or used with a web server, the simplest version of a Hello World program can be written like this, with the closing tag omitted as preferred in files containing pure PHP code[54] (prior to PHP 5.4.0, this short syntax for echo() only works with the short_open_tag configuration setting enabled, while for PHP 5.4.0 and later it is always available):[55][56][57]
<?= 'Hello world';
The PHP interpreter only executes PHP code within its delimiters. Anything outside its delimiters is not processed by PHP (although non-PHP text is still subject to control structures described in PHP code). The most common delimiters are <?php
to open and ?>
to close PHP sections. <script language="php">
and </script>
delimiters are also available, as are the shortened forms <?
or <?=
(which is used to echo back a string or variable) and ?>
as well as ASP-style short forms <%
or <%=
and %>
. Short delimiters make script files less portable, since support for them can be disabled in the local PHP configuration, and they are therefore discouraged.[57][58] The purpose of all these delimiters is to separate PHP code from non-PHP code, including HTML.[59]
The first form of delimiters, <?php
and ?>
, in XHTML and other XML documents, creates correctly formed XML "processing instructions".[60] This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.
Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. PHP 5 introduced type hinting that allows functions to force their parameters to be objects of a specific class, arrays, interfaces or callback functions. However, type hints can not be used with scalar types such as integer or string.[61]
Unlike function and class names, variable names are case sensitive. Both double-quoted (""
) and heredoc strings provide the ability to interpolate a variable's value into the string.[62] PHP treats newlines as whitespace in the manner of a free-form language (except when inside string quotes), and statements are terminated by a semicolon.[63] PHP has three types of comment syntax: /* */
marks block and inline comments; //
as well as #
are used for one-line comments.[64] The echo statement is one of several facilities PHP provides to output text, e.g., to a web browser.
In terms of keywords and language syntax, PHP is similar to most high level languages that follow the C style syntax. if
conditions, for
and while
loops, and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.
Data types
PHP stores whole numbers in a platform-dependent range, either a 64-bit or 32-bit signed integer equivalent to the C-language long type. Unsigned integers are converted to signed values in certain situations; this behavior is different from other programming languages.[65] Integer variables can be assigned using decimal (positive and negative), octal, hexadecimal, and binary notations.
Floating point numbers are also stored in a platform-specific range. They can be specified using floating point notation, or two forms of scientific notation.[66] PHP has a native Boolean type that is similar to the native Boolean types in Java and C++. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in Perl and C++.[66]
The null data type represents a variable that has no value; NULL is the only allowed value for this data type.[66]
Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources.[66]
Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in hashes with both keys and values, and the two can be intermingled.[66] PHP also supports strings, which can be used with single quotes, double quotes, nowdoc or heredoc syntax.[67]
The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.[68]
Functions
PHP has hundreds of functions provided by the core language functionality and thousands more available via various extensions; these functions are well documented in the online PHP documentation.[69] However, the built-in library has a wide variety of naming conventions and associated inconsistencies, as described under history above.
Additional functions can be defined by the developer:
function myAge($birthYear) // defines a function, this one is named "myAge"
{
$yearsOld = date('Y') - $birthYear; // calculates the age
return $yearsOld . ' year' . ($yearsOld != 1 ? 's' : ''); // returns the age in a descriptive form
}
echo 'I am currently ' . myAge(1981) . ' old.'; // outputs the text concatenated
// with the return value of myAge()
// As the result of this syntax, myAge() is called.
// In 2014, the output of this sample program will be 'I am currently 33 years old.'
In PHP, normal functions are not first-class and can only be referenced by their name directly, or dynamically by a variable containing the name of the function (referred to as "variable functions"). User-defined functions can be created at any time without being prototyped.[69][70] Functions can be defined inside code blocks, permitting a run-time decision as to whether or not a function should be defined. Function calls must use parentheses, with the exception of zero-argument class constructor functions called with the PHP new
operator, where parentheses are optional.
Until PHP 5.3, support for true anonymous functions or closures did not exist in PHP. While create_function()
exists since PHP 4.0.1, it is merely a thin wrapper around eval()
that allows normal PHP functions to be created during program execution.[71] Also, support for variable functions allows normal PHP functions to be used, for example, as callbacks or within function tables.[70] PHP 5.3 added support for closures, which are true anonymous, first-class functions,[72] whose syntax can be seen in the following example:
function getAdder($x)
{
return function($y) use ($x)
{
return $x + $y;
};
}
$adder = getAdder(8);
echo $adder(2); // prints "10"
In the example above, getAdder()
function creates a closure using passed argument $x
(the keyword use
imports a variable from the lexical context), which takes an additional argument $y
, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as a parameter to other functions, etc.[73]
The goto
flow control statement is used as in the following example:
function lock()
{
$file = fopen('file.txt', 'r+');
retry:
if (!flock($file, LOCK_EX | LOCK_NB))
goto retry;
fwrite($file, 'Success!');
fclose($file);
}
When flock()
is called, PHP opens a file and tries to lock it. The target label retry:
defines the point to which execution should return if flock()
is unsuccessful and goto retry;
is called. The goto
statement is restricted and requires that the target label be in the same file and context.
The goto
statement has been supported since PHP 5.3.
Objects
Basic object-oriented programming functionality was added in PHP 3 and improved in PHP 4.[6] Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance.[74] In previous versions of PHP, objects were handled like value types.[74] The drawback of this method was that the whole object was copied when a variable was assigned or passed as a parameter to a method. In the new approach, objects are referenced by handle, and not by value.
PHP 5 introduced private and protected member variables and methods, along with abstract classes, final classes, abstract methods, and final methods. It also introduced a standard way of declaring constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception handling model. Furthermore, PHP 5 added interfaces and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach
language construct. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference at compile time.[75]
If the developer creates a copy of an object using the reserved word clone
, the Zend engine will check whether a __clone()
method has been defined. If not, it will call a default __clone()
which will copy the object's properties. If a __clone()
method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so the programmer can start with a by-value replica of the source object and only override properties that need to be changed.[76]
The following is a basic example of object-oriented programming in PHP:
class Person
{
public $firstName;
public $lastName;
public function __construct($firstName, $lastName = '') { // optional second argument
$this->firstName = $firstName;
$this->lastName = $lastName;
}
public function greet() {
return 'Hello, my name is ' . $this->firstName .
(($this->lastName != '') ? (' ' . $this->lastName) : '') . '.';
}
public static function staticGreet($firstName, $lastName) {
return 'Hello, my name is ' . $firstName . ' ' . $lastName . '.';
}
}
$he = new Person('John', 'Smith');
$she = new Person('Sally', 'Davis');
$other = new Person('iAmine');
echo $he->greet(); // prints "Hello, my name is John Smith."
echo '<br />';
echo $she->greet(); // prints "Hello, my name is Sally Davis."
echo '<br />';
echo $other->greet(); // prints "Hello, my name is iAmine."
echo '<br />';
echo Person::staticGreet('Jane', 'Doe'); // prints "Hello, my name is Jane Doe."
The visibility of PHP properties and methods is defined using the keywords public
, private
, and protected
. The default is public, if only var is used; var
is a synonym for public
. Items declared public
can be accessed everywhere. protected
limits access to inherited classes (and to the class that defines the item). private
limits visibility only to the class that defines the item.[77] Objects of the same type have access to each other's private and protected members even though they are not the same instance. PHP's member visibility features have sometimes been described as "highly useful."[78] However, they have also sometimes been described as "at best irrelevant and at worst positively harmful."[79]
Implementations
The original, only complete and most widely used PHP implementation is powered by the Zend Engine and known simply as PHP. To disambiguate it from other implementations, it is sometimes unofficially referred to as "Zend PHP". The Zend Engine compiles PHP source code on-the-fly into an internal format that it can execute, thus it works as an interpreter.[80][81] It is also the "reference implementation" of PHP, as PHP has no formal specification, and so the semantics of Zend PHP define the semantics of PHP itself. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility.
PHP's single-request-per-script-execution model, and the fact the Zend Engine is an interpreter, led to inefficiency. As a result, various products have been developed to help improve PHP performance. In order to speed up execution time and not have to compile the PHP source code every time the web page is accessed, PHP scripts can also be deployed in the PHP engine's internal format by using an opcode cache, which works by caching the compiled form of a PHP script (opcodes) in shared memory to avoid the overhead of parsing and compiling the code every time the script runs. An opcode cache, Zend Opcache, is built into PHP since version 5.5.[82] Another example of a widely used opcode cache is the Alternative PHP Cache (APC), which is available as a PECL extension.[83]
While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these are compilers or support JIT compilation, and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility. Alternative implementations include the following:
- HipHop Virtual Machine (HHVM) – developed at Facebook and available as open source, it converts PHP code into a high-level bytecode (commonly known as an intermediate language), which is then translated into x86-64 machine code dynamically at runtime by a just-in-time (JIT) compiler, resulting in up to 6× performance improvements.[84]
- Parrot – a virtual machine designed to run dynamic languages efficiently; Pipp transforms the PHP source code into the Parrot intermediate representation, which is then translated into the Parrot's bytecode and executed by the virtual machine.
- Phalanger – compiles PHP into Common Intermediate Language (CIL) bytecode
- HipHop – developed at Facebook and available as open source, it transforms the PHP scripts into C++ code and then compiles the resulting code, reducing the server load up to 50%. In early 2013, Facebook deprecated it in favor of HHVM due to multiple reasons, including deployment difficulties and lack of support for the whole PHP language, including the create_function() and eval() constructs.[85]
Licensing
PHP is free software released under the PHP License, which stipulates that:[86]
Products derived from this software may not be called "PHP", nor may "PHP" appear in their name, without prior written permission from group@php.net. You may indicate that your software works in conjunction with PHP by saying "Foo for PHP" instead of calling it "PHP Foo" or "phpfoo".
This restriction on use of the name PHP makes it incompatible with the GNU General Public License (GPL).[87]
Development and community
PHP includes free and open source libraries with the core build. PHP is a fundamentally Internet-aware system with modules built in for accessing File Transfer Protocol (FTP) servers, many database servers, embedded SQL libraries such as embedded PostgreSQL, MySQL, Microsoft SQL Server and SQLite, LDAP servers, and others. Many functions familiar to C programmers such as those in the stdio family are available in the standard PHP build.[88]
PHP allows developers to write extensions in C to add functionality to the PHP language. PHP extensions can be compiled statically into PHP or loaded dynamically at runtime. Numerous extensions have been written to add support for the Windows API, process management on Unix-like operating systems, multibyte strings (Unicode), cURL, and several popular compression formats. Other PHP features made available through extensions include integration with IRC, dynamic generation of images and Adobe Flash content, PHP Data Objects (PDO) as an abstraction layer used for accessing databases,[89][90][91][92][93][94][95] and even speech synthesis. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions.[96] The PHP Extension Community Library (PECL) project is a repository for extensions to the PHP language.[97]
Some other projects, such as Zephir, provide the ability for PHP extensions to be created in a high-level language and compiled into native PHP extensions. Such an approach, instead of writing PHP extensions directly in C, simplifies the development of extensions and reduces the time required for programming and testing.[98]
Zend Technologies provides a certification exam for programmers to become certified PHP developers.
Installation and configuration
There are two primary ways for adding support for PHP to a web server – as a native web server module, or as a CGI executable. PHP has a direct module interface called Server Application Programming Interface (SAPI), which is supported by many web servers including Apache HTTP Server, Microsoft IIS, Netscape (now defunct) and iPlanet. Some other web servers, such as OmniHTTPd, support the Internet Server Application Programming Interface (ISAPI), which is a Microsoft's web server module interface. If PHP has no module support for a web server, it can always be used as a Common Gateway Interface (CGI) or FastCGI processor; in that case, the web server is configured to use PHP's CGI executable to process all requests to PHP files.[99]
PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the official PHP distribution since version 5.3.3.[100] When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers.[101]
When using PHP for command-line scripting, a PHP command-line interface (CLI) executable is needed. PHP supports a CLI SAPI as of PHP 4.3.0.[102] The main focus of this SAPI is developing shell applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviors.[103]
PHP can also be used for writing desktop graphical user interface (GUI) applications, by using the PHP-GTK extension. PHP-GTK is not included in the official PHP distribution,[99] and as an extension it can be used only with PHP versions 5.1.0 and newer. The most common way of installing PHP-GTK is compiling it from the source code.[104]
When PHP is installed and used in cloud environments, software development kits (SDKs) are provided for using cloud-specific features. For example:
- Amazon Web Services provides the AWS SDK for PHP[105]
- Windows Azure can be used with the Windows Azure SDK for PHP.[106]
Numerous configuration options are supported, affecting both core PHP features and extensions.[107][108] Configuration file php.ini
is searched for in different locations, depending on the way PHP is used.[109] The configuration file is split into various sections,[110] while some of the configuration options can be also set within the web server configuration.[111]
Use
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/LAMP_software_bundle.svg/400px-LAMP_software_bundle.svg.png)
PHP is a general-purpose scripting language that is especially suited to server-side web development, in which case PHP generally runs on a web server. Any PHP code in a requested file is executed by the PHP runtime, usually to create dynamic web page content or dynamic images used on websites or elsewhere.[112] It can also be used for command-line scripting and client-side graphical user interface (GUI) applications. PHP can be deployed on most web servers, many operating systems and platforms, and can be used with many relational database management systems (RDBMS). Most web hosting providers support PHP for use by their clients. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use.[9]
PHP acts primarily as a filter,[113] taking input from a file or stream containing text and/or PHP instructions and outputting another stream of data. Most commonly the output will be HTML, although it could be JSON, XML or binary data such as image or audio formats. Since PHP 4, the PHP parser compiles input to produce bytecode for processing by the Zend Engine, giving improved performance over its interpreter predecessor.[114]
Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting,[115] and it is similar to other server-side scripting languages that provide dynamic content from a web server to a client, such as Microsoft's ASP.NET, Sun Microsystems' JavaServer Pages,[116] and mod_perl. PHP has also attracted the development of many software frameworks that provide building blocks and a design structure to promote rapid application development (RAD). Some of these include PRADO, CakePHP, Symfony, CodeIgniter, Laravel, Yii Framework, and Zend Framework, offering features similar to other web application frameworks.
The LAMP architecture has become popular in the web industry as a way of deploying web applications.[117] PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer to Python, Perl, or some mix of the three. Similar packages, WAMP and MAMP, are also available for Windows and OS X, with the first letter standing for the respective operating system. Although both PHP and Apache are provided as part of the Mac OS X base install, users of these packages seek a simpler installation mechanism that can be more easily kept up to date.
As of April 2007[update], over 20 million Internet domains had web services hosted on servers with PHP installed and mod_php was recorded as the most popular Apache HTTP Server module.[118] As of October 2010[update], PHP was used as the server-side programming language on 75% of all websites whose server-side programming language was known[119] (as of February 2014[update], the percentage had reached 82%[119]), and PHP was the most-used open source software within enterprises.[120] Web content management systems written in PHP include MediaWiki,[121] Joomla, eZ Publish, SilverStripe,[122] WordPress,[123] Drupal,[124] Moodle,[125] the user-facing portion of Facebook,[126] and Digg.[127]
For specific and more advanced usage scenarios, PHP offers a well defined and documented way for writing custom extensions in C or C++.[128][129][130][131][132][133][134] Besides extending the language itself in form of additional libraries, extensions are providing a way for improving execution speed where it is critical and there is room for improvements by using a true compiled language.[135][136] PHP also offers well defined ways for embedding itself into other software projects. That way PHP can be easily used as an internal scripting language for another project, also providing tight interfacing with the project's specific internal data structures.[137]
PHP received mixed reviews due to lacking support for multithreading at the core language level,[138] though using threads is made possible by the "pthreads" PECL extension.[139][140]
Security
In 2013, 9% of all vulnerabilities listed by the National Vulnerability Database were linked to PHP;[141] historically, about 30% of all vulnerabilities listed since 1996 in this database are linked to PHP. Technical security flaws of the language itself or of its core libraries are not frequent (22 in 2009, about 1% of the total although PHP applies to about 20% of programs listed).[142] Recognizing that programmers make mistakes, some languages include taint checking to automatically detect the lack of input validation which induces many issues. Such a feature is being developed for PHP,[143] but its inclusion into a release has been rejected several times in the past.[144][145]
There are advanced protection patches such as Suhosin and Hardening-Patch, especially designed for web hosting environments.[146]
There are certain language features and configuration parameters (primarily the default values for such runtime settings) that make PHP prone to security issues. Among these, magic_quotes_gpc and register_globals[147] configuration directives are the best known; the latter made any URL parameters become PHP variables, opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script. Support for "magic quotes" and "register globals" has been deprecated as of PHP 5.3.0, and removed as of PHP 5.4.0.[147][148]
Another example for the runtime settings vulnerability comes from failing to disable PHP execution (via engine configuration directive)[149] for the directory where uploaded images are stored; leaving the default settings can result in execution of malicious PHP code embedded within the uploaded images.[150][151][152] Also, leaving enabled the dynamic loading of PHP extensions (via enable_dl configuration directive)[153] in a shared web hosting environment can lead to security issues.[154][155]
Also, implied type conversions that result in incompatible values being treated as identical against the programmer's intent can lead to security issues. For example, the result of 0e1234 == 0 comparison will be true because the first compared value will be treated as scientific notation of a number (0×101234) with value of zero. This feature resulted in authentication vulnerabilities in Simple Machines Forum,[156] Typo3[157] and phpBB[158] when MD5 password hashes were compared. Instead, identity operator (===) should be used; 0e1234 === 0 results in false.[159]
See also
- PEAR (PHP Extension and Application Repository)
- PHP Extension Community Library (PECL)
- PHP accelerator
- List of PHP accelerators
- List of AMP packages
- List of PHP editors
- PHP-GTK
- Template processor
- XAMPP (Free and open source cross-platform web server solution stack package)
- Zend Server
- Hack (programming language)
- Comparison of programming languages
- Comparison of web application frameworks
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External links
- Free compilers and interpreters
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