PHP code is usually processed on aweb server by a PHPinterpreter implemented as amodule, adaemon or aCommon Gateway Interface (CGI) executable. On a web server, the result of the interpreted and executed PHP code—which may be any type of data, such as generatedHTML orbinary image data—can form the whole or part of anHTTP response. Variousweb template systems, webcontent management systems, andweb frameworks exist that can be employed to orchestrate or facilitate the generation of that response. Additionally, PHP can be used for programming tasks outside the web context, though non-web uses are rare. PHP code can also be directly executed from thecommand line.
The PHP language at first evolved without a writtenformal specification or standard, with the originalimplementation acting as thede facto standard that other implementations aimed to follow.
<!--include /text/header.html--><!--getenv HTTP_USER_AGENT--><!--if substr $exec_result Mozilla--> Hey, you are using Netscape!<p><!--endif--><!--sql database select * from table where user='$username'--><!--ifless $numentries 1--> Sorry, that record does not exist<p><!--endif exit--> Welcome<!--$user-->!<p> You have<!--$index:0--> credits left in your account.<p><!--include /text/footer.html-->
PHP/FI could be used to build simple,dynamic web applications. To acceleratebug reporting and improve the code, Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" on theUsenet discussion groupcomp.infosystems.www.authoring.cgi on 8 June 1995.[1][19] This release included basic functionality such asPerl-like variables, form handling, and the ability to embedHTML. By this point, thesyntax had changed to resemble that ofPerl, but was simpler, more limited, and less consistent.[12][11]
Early PHP was never intended to be a newprogramming language; rather, it 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."[20] A development team began to form and, after months of work andbeta testing, officially released PHP/FI 2 in November 1997.[21]
The fact that PHP was not originally designed, but instead was developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters.[22] In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping",[23] while in some very early versions of PHP the length of the function names was used internally as ahash function, so names were chosen to improve the distribution ofhash values.[24]
On 22 May 2000, PHP 4.0, powered by the Zend Engine 1.0, was released.[11] By August 2008, this branch had reached version 4.4.9. PHP 4 is now no longer under development and nor are any security updates planned to be released.[27][28]
On 1 July 2004, PHP 5.0 was released, powered by the new Zend Engine 2.0.[11] PHP 5.0 included significant changes to the language, most notably an overhauled approach toobject-oriented programming, as well asiterators andexceptions.[29]
PHP 5.1 and PHP 5.2 were released the following years, adding smaller improvements and new features, such as the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases) In 2008, PHP 5.x became the only stable version under development.
Many high-profile open-source projects ceased to support PHP 4 in new code from February 5, 2008, because of the GoPHP5 initiative,[30] provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.[31][32]
PHP's native string functions worked only on raw bytes, making use withmultibyte character encodings difficult.[33][34] In 2005, a project headed by Andrei Zmievski was initiated to bring nativeUnicode support throughout PHP, by embedding theInternational Components for Unicode (ICU) library, and representing text strings asUTF-16 internally.[35] 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.[36]
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.[37] As a result, a PHP 5.3 release was created in 2009, and in March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared to contain most remaining non-Unicode features from PHP 6.[38] Initial hopes were that a new plan would be formed for Unicode integration, but by 2014 none had been adopted.[citation needed]
Because it contained features originally intended to be part of 6.0, PHP 5.3 was a significant release, adding support fornamespaces,closures,late static binding,[39][40] and many fixes and improvements to standard functions.
With the Unicode branch officially abandoned, a new release process was adopted in 2011, planning a yearly release cycle, and a clear distinction between "feature releases" (x.y.z to x.y+1.z) and "major releases" (x.y.z to x+1.0.0).[41] Remaining features which had been planned for the 6.0 release were included in PHP 5.4, released in March 2012, such astrait support and a new "short array syntax". This was followed by more incremental changes in PHP 5.5 (June 2013) and 5.6 (August 2014).
For PHP versions 5.3 and 5.4, the only availableMicrosoft Windows binary distributions were 32-bitIA-32 builds,[42][43] requiring Windows 32-bit compatibility mode while usingInternet Information Services (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bitx86-64 builds available for Microsoft Windows.[44]
Official security support for PHP 5.6 ended on 31 December 2018.[45]
During 2014 and 2015, a new major PHP version was developed, PHP 7.0. The numbering of this version involved some debate among internal developers.[46] While the PHP 6 Unicode experiments had never been released, several articles and book titles referenced the PHP 6 names, which might have caused confusion if a new release were to reuse the name.[47] After a vote, the name PHP 7 was chosen.[48]
The foundation of PHP 7.0 was a PHPbranch that was originally dubbedPHP next generation (phpng). It was written by Dmitry Stogov, Xinchen Hui and Nikita Popov,[49] and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility.[50] By 14 July 2014,WordPress-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng make it easier to improve performance in future versions, as more compact data structures and other changes are seen as better suited for a successful migration to ajust-in-time (JIT) compiler.[51] Because of the significant changes, the reworked Zend Engine was calledZend Engine 3, succeeding Zend Engine 2 used in PHP 5.x.[52]
PHP 7.0 also included changes which were not backwards compatible, as allowed for "major versions" under theversioning scheme agreed in 2011.[41] Changes to the core language included a more consistent handling of variable dereferencing,[53] a more predictable behavior of theforeach statement,[54] and platform consistency ofbitwise shifts[55] and floating-point to integer conversion.[55][56] Several unmaintained or deprecatedserver application programming interfaces (SAPIs) and extensions were removed from the PHP core, most notably the legacymysql extension.[57] Other legacy features were also removed, such as ASP-style delimiters<% and%> and<script language="php"> ... </script>.[58]
PHP 7.0 marked the beginning of an expansion in PHP's type system. In PHP 5.x, only function parameters could have type declarations, but this was extended to function return types in 7.0.,[59] and object properties in 7.4[60] The types expressible also expanded, withscalar types (integer, float, string, and boolean) in 7.0;[61]iterable type,[62] nullable types,[63] andvoid return type.[64] all in 7.1; and theobject type in 7.2[65]
Other changes in this period aimed to add expressiveness to the language, such as the?? (null coalesce)[66]and<=> "spaceship"three-way comparison[67] operators in 7.0; new syntax for array derefencing[68] and catching multiple exception types[69] in PHP 7.1; more flexibleHeredoc and Nowdoc syntax[70] in 7.3; and the null-coalescing assignment operator[71] in 7.4.
PHP 8.0 was released on 26 November 2020, as a major version withbreaking changes from previous versions.[72][73]
One of the most high-profile changes was the addition of aJIT compiler, which can provide substantial performance improvements for some use cases.[74][75] Substantial improvements were expected more for mathematical-type operations than for common web-development use cases.[76] Additionally, the performance advantage of the JIT compiler provides the potential to move some code from C to PHP.[77]
A significant addition to the language in 8.0 isattributes, which allow metadata to be added to program elements such as classes, methods, and parameters.[72] Later versions added built-in attributes which change the behaviour of the language, such as the#[\SensitiveParameter] attribute in PHP 8.2,[78]#[\Override] in PHP 8.3,[79]#[\Deprecated] in PHP 8.4,[80] and the#[\NoDiscard] and#[\DelayedTargetValidation] attributes in PHP 8.5.[81][82][83]
A significant extension to the language's type system is the addition of composite types: union types in PHP 8.0 (e.g.int|string meaning "either integer or string),[84] intersection types in PHP 8.1 (e.g.Traversable&Countable meaning the value must implement both theTraversable andCountable interfaces),[85] anddisjunctive normal form (DNF) types in PHP 8.2 (unions of intersections, such asarray|(Traversable&Countable)).[86] Additional special type keywords have been added, such asmixed andstatic in PHP 8.0,[72]never (abottom type indicating that a function never returns) in PHP 8.1,[87] andnull,false, andtrue as stand-alone types in PHP 8.2.[88][89]
The addition of a rich type system is part of a general trend towards a stricter language, and PHP 8.0 included breaking changes to the handling of string to number comparisons,[90] numeric strings,[91] and incompatible method signatures.[92] Later versions have introduced deprecation notices for behaviour which is planned as a breaking change in a future major version, such as passingnull to non-nullable internal function parameters[93] and referring to properties which have not been declared on the class.[94]
Officially called "Personal Home Page Tools (PHP Tools)". This is the first use of the name "PHP".[11]
Unsupported: 2.0
1 November 1997
Officially called "PHP/FI 2.0". The first release that could be characterised as PHP, being a standalone language with many features that have endured to the present day.
Disabledregister_globals by default. Data received over the network is not inserted directly into theglobal namespace anymore, closing possible security holes in applications.[97]
Performance improvements with the introduction of compiler variables in a re-engineered PHP Engine.[105] Added PHP Data Objects (PDO) as a consistent interface for accessing databases.[107]
Namespace support;late static bindings, jump label (limitedgoto),anonymous functions,closures, PHP archives (phar),garbage collection for circular references, improvedWindows support, sqlite3, mysqlnd as a replacement for libmysql as the underlying library for the extensions that work withMySQL, fileinfo as a replacement for mime_magic for betterMIME support, the Internationalization extension, and deprecation of the ereg extension.
Trait support, short array syntax support. Removed items:register_globals,safe_mode,allow_call_time_pass_reference,session_register(),session_unregister() andsession_is_registered(). Built-in web server.[111] Improvements to features and performance, reduced memory requirements.
Constant scalar expressions,variadic functions, argument unpacking, new exponentiation operator, extensions of theuse statement for functions and constants, newphpdbg debugger as a SAPI module, and other smaller improvements.[116]
6.x
Not released
—N/a
Abandoned version of PHP that planned to include native Unicode support.[117][118]
Zend Engine 3 (performance improvements[51] and 64-bit integer support on Windows[120]), uniform variable syntax,[53]AST-based compilation process,[121] addedClosure::call(),[122] bitwise shift consistency across platforms,[123]?? (null coalesce) operator,[66]Unicode code pointescape syntax,[124] return type declarations,[59] scalar type (integer, float, string and boolean) declarations,[61]<=> "spaceship"three-way comparison operator,[67]generator delegation,[125]anonymous classes,[126] simpler and more consistently availableCSPRNG API,[127] replacement of many remaining internal PHP "errors" with the more modernexceptions,[128] and shorthand syntax for importing multiple items from a namespace.[129]
FlexibleHeredoc and Nowdoc syntax,[70] support for reference assignment and array deconstruction withlist(),[135] PCRE2 support,[136]hrtime function[137]
Just-In-Time (JIT) compilation,[150] arrays starting with a negative index,[151] stricter/saner language semantics (validation for abstract trait methods),[152] saner string to number comparisons,[90] saner numeric strings,[91]TypeError on invalid arithmetic/bitwise operators,[153] reclassification of various engine errors,[154] consistent type errors for internal functions,[155] fatal error for incompatible method signatures,[92] locale-independent float to string conversion,[156] variable syntax tweaks,[157] attributes,[158][159][160][161] named arguments,[162] match expression,[163] constructor property promotion,[164] union types,[84]mixed type,[165] static return type,[166] nullsafe operator,[167] non-capturing catches,[168]throw expression,[169] JSON extension is always available.[170]
Readonly classes,[180]null,false, andtrue as stand-alone types,[88][89] locale-independent case conversion,[181] disjunctive normal form types,[86] constants in traits[182]
Beginning on 28 June 2011, the PHP Development Team implemented a timeline for the release of new versions of PHP.[41] Under this system, at least one release should occur every month. Once per year, a minor release should occur which may include new features. Every minor release should at least be supported for two years with security and bug fixes, followed by at least one year of only security fixes, for a total of a three-year release process for every minor release. No new features, unless small and self-contained, are to be introduced into a minor release during the three-year release process. A 2024 RFC extended the length of the security fix only period to two years, fixed all end of life dates to 31 December, and removed the exception that allowed for "small and self-contained" features to be introduced in patch versions.[192]
W3Techs reports that as of November 2025[update] (about three years since PHP 7 was discontinued and 23 months after the PHP 8.3 release), unsupported versions such as PHP 7 are still used by well over half of PHP websites, which are outdated and known to be insecure.[193][194] Those included the 9.7% of PHP websites using the even more outdated (discontinued for 7 years) and insecure PHP 5, released over two decades ago.
The mascot of the PHP project is theelePHPant, a blueelephant with the PHP logo on its side, designed by Vincent Pontier[195] in 1998.[196] "The (PHP) letters were forming the shape of an elephant if viewed in a sideways angle."[197]
The elePHPant is sometimes differently coloured when inplush toy form.[198] Many variations of this physical mascot have been made over the years. Only the elePHPants based on the original design by Vincent Pontier are considered official by the community.[199] These are collectable and some of them are extremely rare.[200]
The PHP interpreter only executes PHP code within itsdelimiters. Anything outside of its delimiters is not processed by PHP, although the non-PHP text can still be subject tocontrol structures described in PHP code. The most common delimiters are<?php to open and?> to close PHP sections; the shortened form<? also exists. This short delimiter makes script files less portable since support can be disabled in the local PHP configuration and it is therefore discouraged.[201][202] Conversely, there is no recommendation against the echo short tag<?=.[203] Prior to PHP 5.4.0, this short syntax forecho only works with theshort_open_tag configuration setting enabled, while for PHP 5.4.0 and later it is always available.[204][205][201] The purpose of all these delimiters is to separate PHP code from non-PHP content, such asJavaScript code or HTML markup.[206]
The first form of delimiters,<?php and?>, inXHTML and otherXML documents, creates correctly formed XML processing instructions.[207] This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.
Variables areprefixed with adollar symbol, and atype does not need to be specified in advance. PHP 5 introduced type declarations that allow functions to force their parameters to be objects of a specific class, arrays, interfaces orcallback functions. However, before PHP 7, type declarations could not be used with scalar types such as integers or strings.[61]
Below is an example of how PHP variables are declared and initialized.
<?php$name='John';// variable of string type being declared and initialized$age=18;// variable of integer type being declared and initialized$height=5.3;// variable of double type being declared and initializedecho$name.' is '.$height."m tall\n";// concatenating variables and stringsecho"$name is$age years old.";// interpolating variables to string?>
Unlike function and class names, variable names are case-sensitive. Both double-quoted ("") andheredoc strings provide the ability to interpolate a variable's value into the string.[208] PHP treatsnewlines aswhitespace in the manner of afree-form language, and statements are terminated by a semicolon.[209] PHP has three types ofcomment syntax:/* */ marks block and inline comments;// or# are used for one-line comments.[210] Theecho statement is one of several facilities PHP provides to output text.[citation needed]
In terms of keywords and language syntax, PHP is similar to C-style syntax.if conditions,for andwhile loops and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.[citation needed]
PHP isloosely typed. It stores integers in a platform-dependent range, either as a 32, 64 or 128-bitsignedinteger equivalent to theC-language long type. Unsigned integers are converted to signed values in certain situations, which is different behaviour to many other programming languages.[211] Integer variables can be assigned using decimal (positive and negative),octal,hexadecimal, andbinary notations.[212]
Floating-point numbers are also stored in a platform-specific range. They can be specified using floating-point notation, or two forms ofscientific notation.[213] PHP has a nativeBoolean type that is similar to the native Boolean types inJava andC++. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as inPerl and C++.[213]
The null data type represents a variable that has no value;NULL is the only allowed value for this data type.[213]
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.[213]
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 inhashes with both keys and values, and the two can be intermingled.[213] PHP also supportsstrings, which can be used with single quotes, double quotes, nowdoc orheredoc syntax.[214]
TheStandard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.[215]
PHP defines a large array of functions in the core language and many are also available in various extensions; these functions are well documented onlinePHP documentation.[216] However, the built-in library has a wide variety of naming conventions and associated inconsistencies, as described underhistory above.
Custom functions may be defined by the developer:
functionmyAge(int$birthYear):string{// calculate the age by subtracting the birth year from the current year.$yearsOld=date('Y')-$birthYear;// return the age in a descriptive string.return$yearsOld.($yearsOld==1?' year':' years');}echo'I am currently '.myAge(1995).' old.';
As of 2026, the output of the above sample program is "I am currently 31 years old."
In lieu offunction pointers, functions in PHP can be referenced by a string containing their name. In this manner, normal PHP functions can be used, for example, ascallbacks or withinfunction tables.[217] User-defined functions may be created at any time without beingprototyped.[216][217] Functions may be defined inside code blocks, permitting arun-time decision as to whether or not a function should be defined. There is afunction_exists function that determines whether a function with a given name has already been defined. Function calls must use parentheses, with the exception of zero-argument classconstructor functions called with the PHP operatornew, in which case parentheses are optional.[citation needed]
Since PHP 4.0.1create_function(), a thin wrapper aroundeval(), allowed normal PHP functions to be created during program execution; it was deprecated in PHP 7.2 and removed in PHP 8.0[218] in favor of syntax foranonymous functions or "closures"[219] that can capture variables from the surrounding scope, which was added in PHP 5.3. Shorthand arrow syntax was added in PHP 7.4:[220]
functiongetAdder($x){returnfn($y)=>$x+$y;}$adder=getAdder(8);echo$adder(2);// prints "10"
In the example above,getAdder() function creates a closure using passed argument$x, which takes an additional argument$y, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as aparameter to other functions, etc.[221]
Unusually for a dynamically typed language, PHP supports type declarations on function parameters, which are enforced at runtime. This has been supported for classes and interfaces since PHP 5.0, for arrays since PHP 5.1, for "callables" since PHP 5.4, and scalar (integer, float, string and boolean) types since PHP 7.0.[61] PHP 7.0 also has type declarations for function return types, expressed by placing the type name after the list of parameters, preceded by a colon.[59] For example, thegetAdder function from the earlier example could be annotated with types like so in PHP 7:
functiongetAdder(int$x):Closure{returnfn(int$y):int=>$x+$y;}$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
By default, scalar type declarations follow weak typing principles. So, for example, if a parameter's type isint, PHP would allow not only integers, but also convertible numeric strings, floats or Booleans to be passed to that function, and would convert them.[61] However, PHP 7 has a "strict typing" mode which, when used, disallows such conversions for function calls and returns within a file.[61]
Basicobject-oriented programming functionality was added in PHP 3 and improved in PHP 4.[11] This allowed for PHP to gain further abstraction, making creative tasks easier for programmers using the language. Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance.[222] In previous versions of PHP, objects were handled likevalue types.[222] The drawback of this method was that code had to make heavy use of PHP's "reference" variables if it wanted to modify an object it was passed rather than creating a copy of it. In the new approach, objects are referenced byhandle, and not by value.[223]
If the developer creates a copy of an object using the reserved wordclone, 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-valuereplica of the source object and only override properties that need to be changed.[225]
Thevisibility of PHP properties and methods is defined using thekeywordspublic,private, andprotected. The default is public, if onlyvar is used;var is a synonym forpublic. Items declaredpublic can be accessed everywhere.protected limits access toinherited classes (and to the class that defines the item).private limits visibility only to the class that defines the item.[226] Objects of the same type have access to each other's private and protected members even though they are not the same instance.[227]
<?phpabstractclassUser{protectedstring$name;publicfunction__construct(string$name){// make first letter uppercase and the rest lowercase$this->name=ucfirst(strtolower($name));}publicfunctiongreet():string{return"Hello, my name is ".$this->name;}abstractpublicfunctionjob():string;}classStudentextendsUser{publicfunction__construct(string$name,privatestring$course){parent::__construct($name);}publicfunctionjob():string{return"I learn ".$this->course;}}classTeacherextendsUser{publicfunction__construct(string$name,privatearray$teachingCourses){parent::__construct($name);}publicfunctionjob():string{return"I teach ".implode(", ",$this->teachingCourses);}}$students=[newStudent("Alice","Computer Science"),newStudent("Bob","Computer Science"),newStudent("Charlie","Business Studies"),];$teachers=[newTeacher("Dan",["Computer Science","Information Security"]),newTeacher("Erin",["Computer Science","3D Graphics Programming"]),newTeacher("Frankie",["Online Marketing","Business Studies","E-commerce"]),];foreach([$students,$teachers]as$users){echo$users[0]::class."s:\n";array_walk($users,function(User$user){echo"{$user->greet()},{$user->job()}\n";});}
This program outputs the following:
Students:Hello, my name is Alice, I learn Computer ScienceHello, my name is Bob, I learn Computer ScienceHello, my name is Charlie, I learn Business StudiesTeachers:Hello, my name is Dan, I teach Computer Science, Information SecurityHello, my name is Erin, I teach Computer Science, 3D Graphics ProgrammingHello, my name is Frankie, I teach Online Marketing, Business Studies, E-commerce
The only complete PHP implementation is the original, known simply as PHP. It is the most widely used and is powered by theZend Engine. To disambiguate it from other implementations, it is sometimes unofficially called "Zend PHP". The Zend Enginecompiles PHPsource code on-the-fly into an internal format that it can execute, thus it works as aninterpreter.[228][229] 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. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility.[230]
PHP's single-request-per-script-execution model, and the fact that the Zend Engine is an interpreter, leads 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 anopcode cache, which works bycaching the compiled form of a PHP script (opcodes) inshared memory to avoid the overhead ofparsing andcompiling the code every time the script runs. An opcode cache,Zend Opcache, is built into PHP since version 5.5.[231] Another example of a widely used opcode cache is theAlternative PHP Cache (APC), which is available as aPECL extension.[232]
While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these arecompilers or supportJIT compilation, and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility.[citation needed] Alternative implementations include the following:
HHVM (HipHop Virtual Machine) – developed at Facebook and available as open source, it converts PHP code into a high-level bytecode (commonly known as anintermediate language), which is then translated into x86-64 machine code dynamically at runtime by ajust-in-time (JIT) compiler, resulting in up to 6× performance improvements.[233] However, since version 7.2 Zend has outperformed HHVM,[234] and HHVM 3.24 is the last version to officially support PHP.[235]
HipHop – developed at Facebook and available as open source, it transforms the PHP scripts intoC++ code and then compiles the resulting code, reducing the server load up to 50%. In early 2013, Facebook deprecated it in favour of HHVM due to multiple reasons, including deployment difficulties and lack of support for the whole PHP language, including thecreate_function() andeval() constructs.[236]
Parrot – a virtual machine designed to run dynamic languages efficiently; the cross-translator Pipp transforms the PHP source code into theParrot intermediate representation, which is then translated into the Parrot's bytecode and executed by the virtual machine.
PeachPie – a second-generation compiler to .NETCommon Intermediate Language (CIL) bytecode, built on theRoslyn platform; successor of Phalanger, sharing several architectural components
Phalanger – compiles PHP into .Net Common Intermediate Language bytecode; predecessor of PeachPie
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 the use of "PHP" makes the PHP License incompatible with theGNU General Public License (GPL), while the Zend License is incompatible due to an advertising clause similar to that of the originalBSD license.[238]
PHP includes variousfree and open-source libraries in its source distribution or uses them in resulting PHP binary builds. PHP is fundamentally anInternet-aware system with built-in modules for accessingFile Transfer Protocol (FTP) servers and many database servers, includingPostgreSQL,MySQL,Microsoft SQL Server andSQLite (which is an embedded database),LDAP servers, and others. Numerous functions are familiar to C programmers, such as those in thestdio family, are available in standard PHP builds.[239]
PHP allows developers to writeextensions inC 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 theWindows API, process management onUnix-likeoperating systems, multibyte strings (Unicode),cURL, and several popularcompression formats. Other PHP features made available through extensions include integration withInternet Relay Chat (IRC), dynamic generation of images andAdobe Flash content,PHP Data Objects (PDO) as an abstraction layer used for accessing databases,[240][241][242][243][244][245][246] and evenspeech synthesis. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions.[247] ThePHP Extension Community Library (PECL) project is a repository for extensions to the PHP language.[248] Most of the community focuses on web development, and PHP running server side (though also serving JavaScript for the client side), and some exceptional uses are for e.g. standalonegraphical applications (withPHP-GTK unmaintained now for over a decade),[249] and evendrone control.[250]
Some other projects, such asZephir, 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.[251]
Zend Technologies provides aPHP Certification based on PHP 8[253] exam (and previously based on PHP 7 and 5.5) for programmers to become certified PHP developers.
The foundation hires "Core Developers" to work on the PHP language's core repository. Roman Pronskiy, a member of the foundation's board, said that they aim to pay "market salaries" to developers.[259]
The response to the foundation has been largely positive, with commentators praising its role in ensuring the continued development of PHP and helping to stabilise the language's community and popularity.[260][261]
Germany'sSovereign Tech Fund provided more than 200,000 Euros to support the PHP Foundation.[262]
PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the official PHP distribution since version 5.3.3.[264] When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers.[265]
When using PHP for command-line scripting, a PHPcommand-line interface (CLI) executable is needed. PHP supports a CLIserver application programming interface (SAPI) since PHP 4.3.0.[266] The main focus of this SAPI is developingshell applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviours.[267]
PHP has a direct module interface called SAPI for different web servers;[268] in case of PHP 5 and Apache 2.0 on Windows, it is provided in form of aDLL file calledphp5apache2.dll,[269] which is a module that, among other functions, provides an interface between PHP and the web server, implemented in a form that the server understands. This form is what is known as a SAPI.[citation needed]
There are different kinds of SAPIs for various web server extensions. For example, in addition to those listed above, other SAPIs for the PHP language include the Common Gateway Interface and command-line interface.[268][270]
PHP can also be used for writing desktopgraphical user interface (GUI) applications, by using the"PHP Desktop".GitHub. or discontinuedPHP-GTK extension. PHP-GTK is not included in the official PHP distribution,[263] 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 by compiling it from the source code.[271]
When PHP is installed and used incloud environments,software development kits (SDKs) are provided for using cloud-specific features.[272] For example:
Numerous configuration options are supported, affecting both core PHP features and extensions.[275][276] Configuration filephp.ini is searched for in different locations, depending on the way PHP is used.[277] The configuration file is split into various sections,[278] while some of the configuration options can be also set within the web server configuration.[279]
A broad overview of the LAMP software bundle, displayed here together withSquid
PHP is a general-purpose scripting language that is especially suited toserver-sideweb development, in which case PHP generally runs on aweb server. Any PHP code in a requested file isexecuted by the PHP runtime, usually to createdynamic web page content or dynamic images used on websites or elsewhere.[280] It can also be used forcommand-line scripting andclient-sidegraphical user interface (GUI) applications. PHP can be deployed on most web servers, manyoperating systems andplatforms, and can be used with manyrelational database management systems (RDBMS). Mostweb 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.[15]
TheLAMP architecture has become popular in the web industry as a way of deploying web applications.[283] PHP is commonly used as theP in this bundle alongsideLinux,Apache andMySQL, although theP may also refer toPython,Perl, or some mix of the three. Similar packages,WAMP andMAMP, are also available forWindows andmacOS, with the first letter standing for the respective operating system. Although both PHP and Apache are provided as part of the macOS base install, users of these packages seek a simpler installation mechanism that can be more easily kept up to date.[citation needed]
For specific and more advanced usage scenarios, PHP offers a well-defined and documented way for writing custom extensions inC orC++.[284][285][286][287][288][289][290][non-primary source needed] Besides extending the language itself in form of additionallibraries, extensions are providing a way for improving execution speed where it is critical and there is room for improvements by using a truecompiled language.[291][292] PHP also offers well-defined ways for embedding itself into other software projects. That way PHP can be easily used as an internalscripting language for another project, also providing tight interfacing with the project's specific internaldata structures.[293]
PHP received mixed reviews due to lacking support formultithreading at the core language level,[294] though using threads is made possible by the "pthreads"PECL extension.[295][296]
As of January 2013[update], PHP was used in more than 240 millionwebsites (39% of those sampled) and was installed on 2.1 millionweb servers.[303]
As of 20 December 2025[update] (one month after PHP 8.5's release), PHP is used as the server-side programming language on 72.5% of websites where the language could be determined; PHP 8 is the most used version of the language with 54.7% of websites using PHP being on that version, while 35.9% use PHP 7, 9.3% use PHP 5 and 0.1% use PHP 4.[194]
PHP 8 54.7%
PHP 7 35.9%
PHP 5 9.3%
PHP 4 0.1%
Usage share of PHP versions on 20 December 2025: one month after PHP 8.5's release[194][304][305][306][307]
In 2019, 11% of all vulnerabilities listed by theNational Vulnerability Database were linked to PHP;[308] 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).[309] Recognizing that programmers make mistakes, some languages includetaint checking to automatically detect the lack ofinput validation which induces many issues. Such a feature has been proposed for PHP in the past, but either been rejected or the proposal abandoned.[310][311][312]
Third-party projects such asSuhosin[313] and Snuffleupagus[314] aim to remove or change dangerous parts of the language.
Historically, old versions of PHP had some configuration parameters and default values for such runtime settings that made some PHP applications prone to security issues. Among these,magic_quotes_gpc andregister_globals[315] configuration directives were 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" settings has been deprecated since PHP 5.3.0, and removed from PHP 5.4.0.[316]
Another example for the potential runtime-settings vulnerability comes from failing to disable PHP execution (for example by using theengine configuration directive)[317] for the directory where uploaded files are stored; enabling it can result in the execution of malicious code embedded within the uploaded files.[318][319][320] The best practice is to either locate the image directory outside of the document root available to the web server and serve it via an intermediary script or disable PHP execution for the directory which stores the uploaded files.[citation needed]
Also, enabling the dynamic loading of PHP extensions (viaenable_dl configuration directive)[321] in ashared web hosting environment can lead to security issues.[322][323]
Impliedtype conversions that result in different values being treated as equal, sometimes against the programmer's intent, can lead to security issues. For example, the result of the comparison'0e1234' == '0' istrue, because strings that are parsable as numbers are converted to numbers; in this case, the first compared value is treated asscientific notation having the value (0×101234), which is zero. Errors like this resulted in authentication vulnerabilities inSimple Machines Forum,[324]Typo3[325] andphpBB[326] whenMD5password hashes were compared. The recommended way is to usehash_equals() (fortiming attack safety),strcmp or the identity operator (===), as'0e1234' === '0' results infalse.[citation needed]
In a 2013 analysis of over 170,000website defacements, published byZone-H, the most frequently (53%) used technique was the exploitation offile inclusion vulnerability, mostly related to insecure usage of the PHP language constructsinclude,require, andallow_url_fopen.[327][328]
PHP includesrand()[329] andmt_rand()[330] functions which use apseudorandom number generator, and are not cryptographically secure. As of version 8.1, therandom_int() function is included, which uses a cryptographically secure source of randomness provided by the system.[331]
There are two attacks that can be performed over PHP entropy sources: "seed attack" and "state recovery attack".[citation needed] As of 2012, a $250GPU can perform up to 230MD5 calculations per second, while a $750 GPU can perform four times as many calculations at the same time.[332] In combination with a "birthday attack" this can lead to serious security vulnerabilities.[citation needed]
The PHP development team provides official bug fixes for two years following release of each minor version followed by another two years where only security fixes are released.[192] After this, the release is consideredend of life and no longer officially supported.
Extended long-term support beyond this is available from commercial providers, such asZend and others[333][334]
^most of Zend engine underZend Engine License) for PHP 4 and later versions (only; dual-licensedGNU General Public License version 2 or any later version and PHP License for PHP versions 3.0 or earlier.[5]
^ab"PHP RFC: Integer Semantics".php.net. Retrieved2015-05-21.Making NaN and Infinity always become zero when cast to integer means more cross-platform consistency, and is also less surprising than what is currently produces
^Corbet, Jonathan (24 March 2010)."Resetting PHP 6".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.
^Krill, Paul (2014-10-31)."PHP 7 moves full speed ahead".InfoWorld.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.
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