1 History

PHP was originally designed as a small set of Perl scripts, followed by a rewritten set of CGI binaries written in C by Rasmus Lerdorf in 1994 to display his résumé and collect some data, such as how many hits it was generating. Others first used "Personal Home Page Tools" in 1995, when Lerdorf had combined it with his own Form Interpreter to create PHP/FI. Zeev Suraski and Andi Gutmans , two Israeli developers of the Technion - Israel Institute of Technology, rewrote the parser in 1997 and formed the base of PHP 3. They also changed the name to its current recursive form. After months in beta, the development team officially released PHP/FI 2 in November 1997. Public testing of PHP 3 began immediately 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 (a page at www.zend.com [1] states that PHP 3 was powered by Zend Engine 0.5). They also founded Zend Technologies in Ramat Gan, Israel which has since overseen the PHP advances. In May 2000, PHP 4, powered by the Zend Engine 1.0, was released. On July 13, 2004, PHP 5 was released, powered by Zend Engine II (formerly known as Zend Engine 2).

2 Popularity

PHP is currently one of the most popular server-side scripting systems on the Web. It has been widely adopted since the release of version 4, which was the first version powered by the powerful Zend Engine.

One major part of PHP which has helped it become popular is that it is a very loose language; in particular, it is dynamically typed. That is, the rules aren't as strict with variables—they don't have to be declared and they can hold any type of object. Further, unlike many other languages (like C++ and Java), arrays are able to hold objects of varying types, including other arrays. All of this "looseness" makes it very easy to do many things.

According to Netcraft's April 2002 survey, PHP is now the most deployed server-side scripting language, running on around 9 of the 37 million domains in their survey. This is confirmed by PHP's own figures, which show PHP usage (measured on a per-domain basis) growing at around 5% per month. In May 2003, almost 13 million domains were using PHP, based on the same source.[2]

Due to PHP's popularity, a new breed of programmer has emerged – one who is only familiar with PHP, which in turn forced open the door toward a command line interface for PHP, along with support for GUI library such as GTK+ and text mode libraries like ncurses and newt. This is a major step for PHP, because it represents its beginning adoption as a genuine programming language (i.e. running autonomously on a stand-alone machine, as opposed to its original purpose of serving web pages to client machines from a server).

3 Code example

Here is an example that prints out the lyrics for the song 99 Bottles of Beer:

\r\n"; for ($i = 99; $i > 0; $i--) { print "$i bottle" . plural($i) . " of beer on the wall,$l"; // We don't actually need a new print for each line. Let's see: print "$i bottle" . plural($i) . " of beer.$l Take one down, pass it around,$l" . ($i - 1 != 0 ? $i - 1 : "no more") . " bottle" . plural($i - 1) . " of beer on the wall.$l$l"; /* * PHP allows you to put strings on multiple lines, as long as * it eventually finds a semicolon (;) to terminate it. * A period (.) joins (concatenates) strings together. * Variables, the $-symbol things, are parsed (interpolated) * inside double quotation marks ("), but wouldn't be parsed * inside single quotation marks ('). Functions, such as * plural(), are not parsed inside any quotation marks. */ } print "Go to the store,$l buy some more,$l 99 bottles of beer on the wall!"; ?>

4 PHP's libraries

PHP, unlike ASP, has some of the largest free and open-source libraries included with the core build. PHP is a fundamentally Internet-aware system and as such, there are modules built in for accessing FTP servers, all manners of database servers, embedded SQL libraries like embedded MySQL and SQLite, LDAP servers and much more. In addition to this, many familiar C functions such as the printf family are all available in the standard PHP build.

PHP has a wide variety of extensions such as support for the Windows API, process management on UNIX-like operating systems, cURL, and the ZIP/ gzip/ bzip2/ rar/ lzf compression formats. Some of the more unusual features are PDF generation, on-the-fly Macromedia Flash generation, integration with Internet relay chat, generation of dynamic images (where you can change the content that the image has in it), and much more. Some additional extensions are available via the PHP Extension Community Library (PECL).

This is the present list of all officially documented libraries:

Apache BCMath Bzip2 Calendars CCVS COM ClibPDF cURL Cybercash dBase DBM dbx DB++ LDAP DNS DOM XML .NET FrontBase filePro FriBiDi FTP Gettext GD Graphics Library GNU Multi-Precision Library Hyperwave iconv IMAP, POP3 and NNTP Informix

Ingres II Interbase IRC Javax Lotus Notes mailparse MCAL Mcrypt MCVE Mhash Mimetype Functions MS-SQL Ming mnoGoSearch mSQL MySQL Mowhawk muscat Ncurses ODBC Oracle OpenSSL Ovrimos SQL PDF PayFlow Pro POSIX PostgreSQL Printer

Pspell GNU Readline GNU Recode Regular expressions QT-Dom Semaphores SESAM Session Handling Shared Memory SMTP SNMP Sockets SimpleXML SQLite Streams Sybase Token vpopmail WDDX Win32 API XML (Expat) XML-RPC XSLT YAZ Yellow Pages / NIS ZIP Zlib

(Source: PHP.net manual)

5 Object-oriented programming

Up until version 3, PHP had no object-oriented features. In version 3 basic object functionality was added. The same semantics were implemented in PHP 4 as well as pass-by-reference and return-by-reference for objects but the implementation still lacked the powerful and useful features of other object-oriented languages like C++ and Java.

In version 5, which was released in July 2004, PHP's object-oriented functionality has been very much enhanced and is more robust and complete. Here is a summary of some of the changes in PHP 5 (powered by Zend Engine II):

• New Object Model — PHP's handling of objects has been completely rewritten, allowing for better performance and more features. In previous versions of PHP, objects were handled like primitive types (for instance integers and strings). The drawback of this method was that semantically the whole object was copied when a variable was assigned, or pass as a parameter to a method. In the new approach, objects are referenced by handle, and not by value (one can think of a handle as an object's identifier).
• Private and Protected Members — PHP 5 introduces private and protected member variable s, they allow you to define the visibility of class properties.
• Private and Protected Methods — Private and protected methods are also introduced.
• Abstract Classes and Methods — PHP 5 also introduces abstract classes and methods. An abstract method only declares the method's signature and does not provide an implementation. A class that contains abstract methods needs to be declared abstract.
• Interfaces — A class may implement an arbitrary list of interfaces.
• Object Cloning — If the developer asks to create a copy of an object by 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 all of the object's properties. If a __clone() method is defined, then it will be responsible to set the necessary properties in the created object. For convenience, the engine will supply a function that imports all of the properties from the source object, so that they can start with a by-value replica of the source object, and only override properties that need to be changed.
• Unified Constructors — PHP 5 introduces a standard way of declaring constructor methods by calling them by the name __construct().
• Destructors — PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such as Java: When the last reference to an object is destroyed, the object's destructor (a class method named __destruct() that receives no parameters) is called before the object is freed from memory.
• Exceptions — PHP 4 had no exception handling. PHP 5 introduces a exception model similar to that of other programming languages.

More additions and examples of the additions mentioned above are available on this page.

It is should be noted that the static method and class variable features in Zend Engine 2 do not work the way some expect. There is no virtual table feature in the Engine, so the static variables are bound with a name at compile time instead of with a reference. This can lead to unexpected behavior, if you do not understand this.

6 Criticism of PHP

PHP is widely used and widely admired for the tasks it performs. Like any language, however, it has its detractors.

Criticism of PHP also includes those general criticisms ascribed to other scripting programming languages and dynamically typed languages.

Some of the more common criticisms of PHP are as follows:

• The syntax is alleged to be inelegant.
  • Built-in function names have no standard form, with some employing underscores (strip_tags) while others do not (stripslashes).
  • PHP does not enforce the declaration of variables, and variables that have not been initialized can have operations (such as concatenation) performed on them. This leads to security holes with register_globals, as mentioned below.
  • Within sections of the built-in function selection there is little or no consistency regarding argument order (examples: order of subject array and other data for array handling functions, order of needle and haystack in various search functions).
• Some functions have inconsistent output. Statements like This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". can be found in the documentation [3]. This is related to PHP's dynamic typing.
• In some areas the selection of built-in functions is notably incomplete (supplying intersection and union functions, but no full difference function, for example).
• The number of built-in functions is said to be too numerous, with many functions performing the same actions, but with just slightly different data, results, etc. This is said to make it difficult to program in the language without the frequent consultation of a reference work.
  • There are over 3,000 functions, sharing the same global namespace.
• Some default settings and features are said to be confusing and the cause of frequent errors.
  • There is a "magic-quotes" feature that inserts backslashes into user-input strings. The feature was introduced to reduce code written by beginners from being dangerous, (such as in SQL injection attacks), but some criticize it as a frequent cause of improperly displayed text.
• Error messages are said to be confusing; however, this is a common criticism alleged against many, if not all, programming languages.
• Websites written in PHP may have very low security due to certain factors.
  • If register_globals is enabled in PHP's configuration file, users could cause harm by manipulating poorly written code.
  • Global variables such as $_GET, for retrieving information from the URL, can cause problems as users can manipulate poorly written code to make the website not function as intended by the author.

7 Support

PHP is self-supporting with respect to user-support, with PHP users assisting each other through various mediums like CHAT, Forums & Newsgroups, and PHP-Developer web sites.

Direct, one-to-one help is frequently provided free of charge through all of these and other mediums.

Intern, the PHP development team are active participators in such communities, garnering assistance from them in their own development effort (PHP itself) and providing assistance to them as well.

There are many excellent help resources available for the novice PHP programmer.

Worth mentioning are the PHP mailing lists (also available on PHP.net's news server), the Usenet group comp.lang.php, and the IRC channels #php and #phphelp on EFNet, IRCNet, DALnet and other networks. There is also a PHP user group registry. Other IRC channels include #php and #phpfreaks on freenode and also #phpcafe on irc.invisionize.com. Additionally, online forum communities have sprung up around PHP support, such as Devshed and PHPBuilder.

8 Software built with PHP

The following is list of notable software developed using PHP that's not already noted above:

CMSformE
CMSformE
Drupal
Gallery Project
Invision Power Board
Moodle
Mambo Open Source
PhpLDAPadmin
phpMyAdmin	- Used to administer MySQL databases.
PHP-Nuke	- A ContentManagementSystem, or CMS.
PostNuke	- A ContentManagementSystem, or CMS.
phpPgAdmin	-
PhpWiki	-
PmWiki	-
PunBB	-
Smarty	-
Typo3	-
UBB.threads	-
vBulletin	-
WordPress	-
Xaraya	-
XOOPS	-

9 External links

Our sister project, Wikibooks , provides an electronic book on .

9.1 PHP homepage

• Selected sub-pages of php.net:
  • PHP license
  • PHP.net domain-based graph of PHP deployment
  • When using the PHP.net website, access the content you would like to see quickly
• Selected sub-domains of php.net:
  • PHP Extension and Application Repository
  • PHP Extension Community Library
  • PHP-GTK extension providing an object-oriented interface to GTK+ classes and functions

9.2 Advocacy

• Experiences of Using PHP in Large Websites
• Making the Case for PHP at Yahoo! - Michael J. Radwin , Yahoo! Engineer explains why Yahoo! has chosen PHP over Apache mod_include , ASP, ColdFusion, Perl, JSP, Servlets, J2EE, XSLT and ClearSilver
  • Follow-up: One Year of PHP at Yahoo!
• Newsforge report of Netcraft web host survey that says PHP is widely used
• The PHP Scalability Myth - Jack Herrington
• PHP Scales - Chris Shiflett

9.3 Frameworks

• Achievo ATK - Achievo ATK is an open source framework that allows a programmer to focus on business logic rather than HTML coding.
• Ampoliros - Advanced distributed PHP web applications platform, featuring an XML-RPC and SOAP interface.
• Carthag - A PHP 5 native platform for developing enterprise level applications, with J2SE-like API.
• Copix Framework - Developer-oriented open-source PHP framework offering a 5-layer application architecture. Productivity tools, modular architecture, DAO abstraction layer, plugins, xml configuration, ready-made and customizable CMS modules and more (site & documentation in French).
• CreaLabs MerlinWork - Fully OO PHP framework for building stateful web applications.
• DotPHP - Framework that wants to be like ASP.NET.
• Eocene - Simple OO web development framework for PHP and ASP.NET.
• Fusebox for PHP
• iConnect - iConnect is a J2EE like architecture based on the Carthag platform, featuring an EJB-like enterprise application server, a servlets-like web application server and a portlet-like portal server engine.
• Japha - Implementation of the Java API in PHP 5.
• LIMB - LIMB is an OpenSource MVC ( Model-view-controller) CMF with tree/OO based controller.
• LogiCreate - PHP web application server and framework.
• Mojavi Project - Open-source MVC ( Model-view-controller) framework for PHP.
• PEAR - Open-source framework and distribution system for reusable PHP components.
• phpHtmlLib - Set of PHP classes and library functions to help facilitate building, debugging, and rendering of XML, HTML, XHTML, WAP/WML Documents, and SVG (Scalable Vector Graphics) images as well as complex html 'widgets'.
• php.MVC - Open source framework for PHP web applications that implements the MVC design pattern.
• Phrame - Web development platform that encourages application architectures based on the "Model2" approach.
• Plankton Web Application Framework - Integrated collection of classes that provide the building blocks and underlying architecture for an entire PHP web application.
• PRADO - an event-driven and component-based framework for PHP 5, Grand prize winner project of Zend PHP 5 Coding Contest.
• Roadsend SiteManager - Open source web application framework for PHP Developers that includes a framework for code modules and layout templates, database connectivity, SmartForms, sessions, and other tools.
• Web Application Component Toolkit - Modular patterns based framework for creating high performance web applications.
• Yawp - Yet Another Web Programming foundation for PHP applications.

9.4 Integrated development environments and debuggers

9.4.1 IDEs

• ActiveState Komodo
• Dev-PHP
• Dreamweaver MX
• Maguma Workbench - Maguma Workbench goes beyond a typical IDE. Fast, robust and modular, making it the most customizable IDE available (for Linux and Windows).
• NuSphere PHPEd
• PHP Designer 2005 - A Delphi-coded IDE from Michael Pham.
• PHPEclipse - Plug-in for the Eclipse IDE.
• PHPEdit
• Quanta Plus - Does not run on Windows.
• Side
• Xored TruStudio - Also an Eclipse plug-in.
• Zend Studio - A multiplatform (Java based) IDE from the authors of the Zend Engine.

9.4.2 Debuggers (all have profiling features)

• APD - Advanced PHP Debugger
• DBG
• Xdebug

9.5 Security

• PHP Security Workbook - A 55 page workbook on various security topics.
• WACT PHP Application Security Wiki - The Web Application Component Toolkit's wiki page on PHP security resources.

9.6 Tutorials and articles

• Beginner PHP Tutorial, 15 lessons - PHP tutorial that does not assume any programming experience. 15 lessons from installation to processing HTML form data.
• Caching Output in PHP - Tutorial explaining how to improve server performance by caching PHP output.
• Codewalkers.com - Community based on PHP and MySQL development.
• Hotscripts.com PHP scripts for webmasters
• PHP5: Coming Soon to a Webserver Near You - SitePoint overview article about upcoming changes in PHP5 by Harry Fuecks , July 28, 2003
• PHPBuilder - Online resource for PHP developers
• PHP Developer's Network - Online community of beginners, intermediates and advanced programmers
• PHP Freaks - Online resource packed with tutorials, full scripts, and utilities.
• PHP Presents and PHP Conference Material Site - Sites collecting slides of talks given by well known people from the PHP community. The former one is also known as pres2 (version 2 of the latter).
• A PHP 4 Coding Standard
• PHP scripts, documentations and tutorials
• PHP Weblog - PHP developer weblog, with articles, code tutorials, news
• Practical PHP Programming
• Simple tutorial from the official PHP website
• Web Design Reference - Huge mega-reference (over 3,000 links) of information and articles dedicated web design and development. The site advocates web standards, accessibility, usability, PHP and many related topics. It features a listserv and RSS feed for site updates.

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