PHP

Paradigm(s) imperative, functional, object-

oriented, procedural, reflective

Appeared in 1995[1]

Designed by Rasmus Lerdorf

Developer The PHP Group

Stable release 5.5.8 (January 10, 2014)

Typing discipline Dynamic, weak

Major

implementations

Zend Engine, Phalanger,

Quercus, Project Zero, HipHop

Influenced by Perl, C, C++, Java, Tcl[1]

Implementation

language

C

OS Cross-platform

License PHP License

Website www.php.net

(http://www.php.net)

PHP Programming at Wikibooks

PHPFrom Wikipedia, the free encyclopedia

PHP is a server-side scripting language designed for webdevelopment but also used as a general-purposeprogramming language. PHP is now installed on more than

244 million websites and 2.1 million web servers.[2]

Originally created by Rasmus Lerdorf in 1995, the referenceimplementation of PHP is now produced by The PHP

Group.[3] While PHP originally stood for Personal Home

Page,[4] it now stands for PHP: Hypertext Preprocessor, a

recursive backronym.[5]

PHP code is interpreted by a web server with a PHPprocessor module, which generates the resulting web page:PHP commands can be embedded directly into an HTMLsource document rather than calling an external file to processdata. It has also evolved to include a command-line interfacecapability and can be used in standalone graphical

applications.[6]

PHP is free software released under the PHP License. PHPcan be deployed on most web servers and also as astandalone shell on almost every operating system and

platform, free of charge.[7]

Contents

1 History

1.1 Release history

2 Syntax

2.1 Data types

2.2 Functions

2.3 Objects

3 Implementations4 Licensing

5 Development and community

6 Installation and configuration

7 Use

8 Security

9 Criticism

10 See also

11 References

12 External links

Rasmus Lerdorf, who wrote the original Common

Gateway Interface (CGI) component, together with

Andi Gutmans and Zeev Suraski, who rewrote the

parser that formed PHP 3.

History

PHP development began in 1994 when the developerRasmus Lerdorf wrote a series of Common GatewayInterface (CGI) Perl scripts, which he used to maintain hispersonal homepage. The tools performed tasks such as

displaying his résumé and recording his web traffic.[3][8][9]

He rewrote these scripts in C for performance reasons,extending them to add the ability to work with web formsand to communicate with databases, and called thisimplementation "Personal Home Page/Forms Interpreter"or PHP/FI.

PHP/FI could be used to build simple, dynamic webapplications. Lerdorf initially announced the release ofPHP/FI as "Personal Home Page Tools (PHP Tools)

version 1.0" publicly to accelerate bug location and improve the code, on the comp.infosystems.www.authoring.cgi

Usenet discussion group on June 8, 1995.[10][11] This release already had the basic functionality that PHP has as of2013. 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.[3]

Early PHP was not intended to be a new programming language, and grew organically, with Lerdorf noting inretrospect: "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."[12] Adevelopment team began to form and, after months of work and beta testing, officially released PHP/FI 2 inNovember 1997.

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.[3] Afterwards, public testing of PHP 3began, 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.[13] They also founded Zend Technologies in Ramat Gan, Israel.[3]

On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released.[3] 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.[14][15]

On July 13, 2004, PHP 5 was released, powered by the new Zend Engine II.[3] PHP 5 included new features suchas 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.[16] In2008 PHP 5 became the only stable version under development. Late static binding had been missing from PHP

and was added in version 5.3.[17][18]

A new major version has been under development alongside PHP 5 for several years. This version was originallyplanned to be released as PHP 6 as a result of its significant changes, which included plans for full Unicode support.However, Unicode support took developers much longer to implement than originally thought, and the decision was

made in March 2010[19] to move the project to a branch, with features still under development moved to trunk.

Changes in the new code include the removal of register_globals,[20] magic quotes, and safe mode.[14][21] The

reason for the removals was that register_globals had opened security holes by intentionally allowing runtime datainjection, and the use of magic quotes had an unpredictable nature. Instead, to escape characters, magic quotesmay be replaced with the addslashes() function, or more appropriately an escape mechanism specific to the

database vendor itself like mysql_real_escape_string() for MySQL. Functions that will be removed in future

versions and have been deprecated in PHP 5.3 will produce a warning if used.[22]

Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of

the GoPHP5 initiative,[23] provided by a consortium of PHP developers promoting the transition from PHP 4 to

PHP 5.[24][25]

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.[26] For the PHP versions 5.3 and 5.4, the only available

Microsoft Windows binary distributions were 32-bit x86 builds,[27][28] requiring Windows 32-bit compatibilitymode 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.[29]

Release history

Key

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

VersionRelease

date

Supported

until[30] Notes

1.01995-06-08

Officially called "Personal Home Page Tools (PHP Tools)". This is the first

use of the name "PHP".[3]

2.01997-11-01

3.01998-06-

06

2000-10-

20

Development moves from one person to multiple developers. Zeev Suraski

and Andi Gutmans rewrite the base for this version.[3]

4.02000-05-

22

2001-01-

23

Added more advanced two-stage parse/execute tag-parsing system called

the Zend engine.[31]

4.12001-12-

10

2002-03-

12Introduced 'superglobals' ($_GET, $_POST, $_SESSION, etc.)[31]

4.22002-04-

22

2002-09-

06

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.[31]

4.32002-12-

27

2005-03-

31

Introduced the command-line interface (CLI), to supplement the

CGI.[31][32]

4.42005-07-11

2008-08-07

Fixed a memory corruption bug, which required breaking binary

compatibility with extensions compiled against PHP version 4.3.x.[33]

5.02004-07-

13

2005-09-

05Zend Engine II with a new object model.[34]

5.12005-11-24

2006-08-24

Performance improvements with introduction of compiler variables in re-

engineered PHP Engine.[34] Added PHP Data Objects (PDO) as a

consistent interface for accessing databases.[35]

5.22006-11-

02

2011-01-

06Enabled the filter extension by default. Native JSON support.[34]

5.32009-06-30

2014-

07[36]

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 replacementfor 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.

5.42012-03-

01

3 years

after

release[37]

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.[38] Several improvements to existing features, performance and

reduced memory requirements.

5.52013-06-

20

3 yearsafter

release[37]

Support for generators, finally blocks for exceptions handling, Zend

Optimizer+ bundled in official distribution.[39]

5.6No date

set

No date

setInternal operator overloading, GMP changes[40]

6No date

set

No date

set

Although internally commenced in 2007, the development of PHP 6 has

been delayed because in 2010 the developers decided to cancel their

implementation of instance Unicode and introduce UTF-8 support

throughout the entire framework.[41] Most other updates that were intended

for PHP 6 were added to PHP 5.3.0 (namespace support, late static

bindings, lambda functions, closures, goto) and 5.4.0 (traits, closurerebinding) instead.

Beginning on June 28, 2011, the PHP Group began following a timeline for when new versions of PHP will be

released.[37] Under this timeline, at least one release should occur every month. Once per year, a minor releaseshould 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 minorrelease. No new features (unless small and self-contained) will be introduced into a minor release during the 3-yearrelease process.

Syntax

Main article: PHP syntax and semantics

The following Hello world program is written in PHP code embedded in an HTML document:

<!DOCTYPE html><meta charset="utf-8"><title>PHP Test</title><?php echo 'Hello World';?>

However as PHP does not need to be embedded in HTML, or used with a web server, the simplest version of aHello World program can be written like this:

<?= 'Hello world';

The PHP interpreter only executes PHP code within its delimiters. Anything outside its delimiters is not processedby PHP (although non-PHP text is still subject to control structures described in PHP code). The most commondelimiters 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 %>. While short delimiters are used, they make script files

less portable as support for them can be disabled in the PHP configuration (http://wiki.php.net/rfc/shortags), and

they are therefore discouraged.[42] The purpose of all these delimiters is to separate PHP code from non-PHP

code, including HTML.[43]

The first form of delimiters, <?php and ?>, in XHTML and other XML documents, creates correctly formed XML

"processing instructions".[44] This means that the resulting mixture of PHP code and other markup in the server-sidefile is itself well-formed XML.

Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. Unlike functionand 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.[45] 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.[46] PHP has threetypes of comment syntax: /* */ marks block and inline comments; // as well as # are used for one-line

comments.[47] 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 stylesyntax. 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 theC-language long type. Unsigned integers are converted to signed values in certain situations; this behavior is

different from other programming languages.[48] Integer variables can be assigned using decimal (positive andnegative), 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.[49] PHP has a native Boolean type that is similar to the native Booleantypes 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++.[49]

The null data type represents a variable that has no value; NULL is the only allowed value for this data type.[49]

Variables of the "resource" type represent references to resources from external sources. These are typicallycreated by functions from a particular extension, and can only be processed by functions from the same extension;

examples include file, image, and database resources.[49]

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.[49]

PHP also supports strings, which can be used with single quotes, double quotes, nowdoc or heredoc syntax.[50]

The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access

interfaces and classes.[51]

Functions

PHP has hundreds of base functions and thousands more via extensions. These functions are well documented on

the PHP site; however, the built-in library has a wide variety of naming conventions and inconsistencies.[52] Onecause of the inconsistent functions naming is that early versions of PHP internally used string length as a hashfunction for function names, thus using inconsistent names made it easier to get a more uniform distribution of hash

values.[53] PHP currently has no functions for thread programming, although it does support multi process

programming on POSIX systems.[54]

Additional functions can be defined by a developer:

function myFunction() // defines a function, this one is named "myFunction"{ return 'John Doe'; // returns the value 'John Doe'} echo 'My name is ' . myFunction() . '!'; //outputs the text concatenated with the return value of myFunction. // myFunction() is called as the result of this syntax.

// The result of the output will be 'My name is John Doe!'

In PHP 5.2 and earlier, functions are not first-class functions and can only be referenced by their name, directly or

dynamically by a variable containing the name of the function.[55] User-defined functions can be created at any time

without being prototyped.[55] Functions can be defined inside code blocks, permitting a run-time decision as towhether or not a function should be defined. Function calls must use parentheses, with the exception of zeroargument class constructor functions called with the PHP new operator, where parentheses are optional.

PHP supports quasi-anonymous functions through the create_function() function, although they are not true

anonymous functions because anonymous functions are nameless, but functions can only be referenced by name, or

indirectly through a variable $function_name();, in PHP.[55]

PHP gained support for closures in PHP 5.3. That way, true anonymous functions are supported using syntax fromthe following example:

function getAdder($x){ return function($y) use ($x) { return $x + $y; };} $adder = getAdder(8);echo $adder(2); // prints "10"

Here, the 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 otherfunctions, etc. For more details, see the Lambda functions and closures RFC (http://wiki.php.net/rfc/closures).

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.[3] Object handling

was completely rewritten for PHP 5, expanding the feature set and enhancing performance.[56] In previous versions

of PHP, objects were handled like value types.[56] The drawback of this method was that the whole object wascopied when a variable was assigned or passed as a parameter to a method. In the new approach, objects arereferenced 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 specialinterfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be usedwith 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.[57]

If the developer creates a copy of an object using the reserved word clone, the Zend engine will check if a

__clone() method has been defined or not. 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 that the programmer can start with a by-value replica of the source object and only override properties that need

to be changed.[58]

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 . ' ' . $this->lastName . '.'; } public static function staticGreet($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.[59] Objects of the same type have access to each other's private andprotected members even though they are not the same instance. PHP's member visibility features have sometimes

been described as "highly useful."[60] However, they have also sometimes been described as "at best irrelevant and

at worst positively harmful."[61]

Implementations

The PHP language was originally implemented as an interpreter, and this is still the most popular implementation.Several compilers have been developed which decouple the PHP language from the interpreter. Advantages ofcompilation include better execution speed, static analysis, and improved interoperability with code written in other

languages.[62]

PHP compilers of note include Phalanger, which compiles PHP into Common Intermediate Language (CIL)bytecode, and HipHop, developed at Facebook and now available as open source, which transforms the PHPScript into C++, then compiles it, reducing server load up to 50% .

PHP source code is compiled on-the-fly to an internal format that can be executed by the PHP engine.[63][64] Inorder to speed up execution time and not have to compile the PHP source code every time the web page isaccessed, PHP scripts can also be deployed in executable format using a PHP compiler.

Code optimizers aim to enhance the performance of the compiled code by reducing its size, merging redundantinstructions and making other changes that can reduce the execution time. With PHP, there are often opportunities

for code optimization.[65] An example of a code optimizer is the eAccelerator PHP extension.

Another approach for reducing compilation overhead for PHP servers is using an opcode cache. Opcode cacheswork by caching the compiled form of a PHP script (opcodes) in shared memory to avoid the overhead of parsingand compiling the code every time the script runs. An opcode cache, Zend Opcache, is built into PHP since version

5.5.[66] Another example of a widely used opcode cache is the Alternative PHP Cache (APC), which is available

as a PECL extension.[67]

Licensing

PHP is free software released under the PHP License, which stipulates that:[68]

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 inconjunction 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).[69]

Development and community

PHP includes free and open source libraries with the core build. PHP is a fundamentally Internet-aware system withmodules built in for accessing File Transfer Protocol (FTP) servers, many database servers, embedded SQLlibraries 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.[70]

PHP allows developers to write extensions in C to add functionality to the PHP language. These can then becompiled into PHP or loaded dynamically at runtime. Extensions have been written to add support for the WindowsAPI, process management on Unix-like operating systems, multibyte strings (Unicode), cURL, and several popularcompression formats. Other features include integration with IRC, dynamic generation of images and Adobe Flashcontent, and even speech synthesis. The language's core functions such as those dealing with strings and arrays are

also implemented as an extension.[71] The PHP Extension Community Library (PECL) project is a repository for

extensions to the PHP language.[72] PDO - (PHP Data Objects) is an interface for accessing

databases.[73][74][75][76][77][78][79]

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. For many web servers PHP has a directmodule interface called Server Application Programming Interface (SAPI). These web servers include ApacheHTTP Server, Microsoft IIS, Netscape (now defunct) and iPlanet. Some other web servers support the InternetServer Application Programming Interface (ISAPI), Microsoft's web server module interface (OmniHTTPd forexample). If PHP has no module support for a web server, it can always be used as a Common Gateway Interface(CGI) or FastCGI processor. That way, web server is configured to use the CGI executable of PHP to process all

requests to PHP files.[80]

PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the

official PHP distribution since version 5.3.3.[81] When compared to the older FastCGI implementation, it contains

some additional features, mostly useful for heavily loaded web servers.[82]

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.[83] 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.[84]

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,[80] and as an extension it can be used only withPHP versions 5.1.0 and newer. The most common way of installing PHP-GTK is compiling it from the source

Broad overview of the LAMP software bundle, displayed here

together with Squid. A high-performance and high-availability web

server solution providing security in a hostile environment.

code.[85]

When PHP is installed and used in cloud environments, software development kits (SDKs) are provided for usingcloud-specific features. For example:

Amazon Web Services provides the AWS SDK for PHP (http://aws.amazon.com/sdkforphp/)

Windows Azure can be used with the Windows Azure SDK for PHP

(http://www.interoperabilitybridges.com/projects/php-sdk-for-windows-azure.aspx).

Numerous configuration options are supported, affecting both core PHP features and extensions.[86][87]

Configuration file php.ini is searched for in different locations, depending on the way PHP is used.[88]

Configuration file is split into various sections,[89] while some of the configuration options can be also set within the

web server configuration.[90]

Use

PHP is a general-purpose scriptinglanguage that is especially suited to server-side web development where PHPgenerally runs on a web server. Any PHPcode in a requested file is executed by thePHP runtime, usually to create dynamicweb page content or dynamic images used

on websites or elsewhere.[91] It can alsobe used for command-line scripting andclient-side graphical user interface (GUI)applications. PHP can be deployed onmost web servers, many operating systemsand platforms, and can be used with manyrelational database management systems(RDBMS). Most web hosting providerssupport PHP for use by their clients. It isavailable free of charge, and the PHP

Group provides the complete source code for users to build, customize and extend for their own use.[7]

PHP acts primarily as a filter,[92] taking input from a file or stream containing text and/or PHP instructions andoutputting another stream of data; most commonly the output will be HTML, although it could be JSON, XML orimage data, among others useful in web development. Since PHP 4, the PHP parser compiles input to produce

bytecode for processing by the Zend Engine, giving improved performance over its interpreter predecessor.[93]

Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting,[94] and it issimilar 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,[95] and mod_perl. PHP has also attracted thedevelopment of many software frameworks that provide building blocks and a design structure to promote rapidapplication development (RAD). Some of these include PRADO, CakePHP, Symfony, CodeIgniter, Laravel, YiiFramework, 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. PHP iscommonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer toPython, Perl, or some mix of the three. Similar packages are also available for Windows and OS X, then calledWAMP and MAMP, with the first letter standing for the respective operating system. Although both PHP andApache are provided as part of the Mac OS X base install, users of these packages seek a simpler installationmechanism that can be more easily kept up to date.

As of April 2007, 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.[96] PHP is used as the server-side

programming language on 75% of all websites whose server-side programming language is known,[97] and PHP is

the most-used open source software within enterprises.[98] Web content management systems written in PHP

include MediaWiki,[99] Joomla, eZ Publish, SilverStripe,[100] WordPress,[101] Drupal,[102] Moodle,[103] the user-

facing portion of Facebook,[104] and Digg.[105]

For specific and more advanced usage scenarios, PHP offers a well defined and documented way for writing

custom extensions in C or C++.[106][107][108][109][110][111][112] Besides extending the language itself in form ofadditional 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.[113][114] PHP also offers well defined ways forembedding 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.[115]

Security

About 30% of all vulnerabilities listed on the National Vulnerability Database are linked to PHP.[116] Thesevulnerabilities are caused mostly by not following best-practice programming rules. Technical security flaws of the

language itself or of its core libraries are not frequent (23 in 2008, about 1% of the total).[117][118] Recognizing thatprogrammers 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,[119] but its inclusion in a release

has been rejected several times in the past.[120][121]

There are advanced protection patches such as Suhosin and Hardening-Patch, especially designed for web hosting

environments.[122]

Some of the vulnerabilities are induced by improper PHP's runtime configuration. For example, failing to disablePHP execution (http://www.php.net/manual/en/apache.configuration.php#ini.engine) for the directory whereuploaded images are stored, can result in execution of malicious PHP code embedded within uploaded

images.[123][124][125] Another well known example is leaving enabled the dynamic loading(http://www.php.net/manual/en/info.configuration.php#ini.enable-dl) of PHP extensions, in a shared hosting

environment.[126][127]

Criticism

One criticism of PHP is that it was not originally designed, but instead it was developed organically.[12]

Security vulnerabilities can be created by certain language features, induced by some of the historically defaultvalues for their associated runtime settings. Among these settings, magic_quotes_gpc and

register_globals[128] are the best known. The latter made any URL parameters become variables, which—

while making programming easier—could create serious security vulnerabilities, as it allowed an attacker to set thevalue of any 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.[128][129]

Inconsistent naming of functions comes from early versions of PHP, where string length was internally used as a

hash function for function names.[53]

PHP also lacks features such as native Unicode support and multithreading at the core level,[130][131][132] though

using threads is made possible by the pthreads (http://pecl.php.net/package/pthreads) PECL extension.[133]

See also

PEAR (PHP Extension and Application Repository)PECL (PHP Extension Community Library)PHP accelerator

List of PHP acceleratorsList of AMP packages

List of PHP editorsPHP-GTK

Template processorXAMPP (Free and open source cross-platform web server solution stack package)Zend Server

Comparison of programming languagesComparison of web application frameworks

References

1. ̂a b Lerdorf, Rasmus (2007-04-26). "PHP on Hormones – history of PHP presentation by Rasmus Lerdorf givenat the MySQL Conference in Santa Clara, California" (http://itc.conversationsnetwork.org/shows/detail3298.html).The Conversations Network. Retrieved 2009-12-11.

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External links

Official website (http://www.php.net)PHP (http://www.dmoz.org/Computers/Programming/Languages/PHP/) on the Open Directory Project

PHP Reference Manual (http://www.php.net/manual)

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