Php

PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. It also has evolved to include a command-line interface capability and can be used in standalone graphical applications. PHP can be deployed on most web servers and as a standalone interpreter, on almost every operating system and platform free of charge. There is also commercial software such as RadPHP, a rapid application development framework for the PHP language. A competitor to Microsoft's Active Server Pages (ASP) server-side script engine and similar languages, PHP is installed on more than 20 million websites and 1 million web servers.

PHP was originally created by Rasmus Lerdorf in 1995. The main implementation of PHP is now produced by The PHP Group and serves as the de facto standard for PHP as there is no formal specification. PHP is free software released under the PHP License which is incompatible with the GNU General Public License (GPL) due to restrictions on the usage of the term PHP .

While PHP originally stood for "Personal Home Page", it is now said to stand for "PHP: Hypertext Preprocessor", a recursive acronym.

History

PHP development began in 1994 when the Danish/Greenlandic/Canadian programmer Rasmus Lerdorf initially created a set of Perl scripts he called "Personal Home Page Tools" to maintain his personal homepage. The scripts performed tasks such as displaying his résumé and recording his web-page traffic. Lerdorf initially announced the release of PHP on the comp.infosystems.www.authoring.cgi Usenet discussion group on June 8, 1995.

Zeev Suraski and Andi Gutmans, two Israeli developers at the Technion IIT, rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive initialism PHP: Hypertext Preprocessor . Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend Engine in 1999. They also founded Zend Technologies in Ramat Gan, Israel.

In 2008 PHP 5 became the only stable version under development. Late static binding had been missing from PHP and was added in version 5.3.

A new major version has been under development alongside PHP 5 for several years. This version was originally planned 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 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 , magic quotes, and safe mode. The reason for the removals was that register_globals had opened security holes by intentionally allowing runtime data injection, and the use of magic quotes had an unpredictable nature. Instead, to escape characters, magic quotes may 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.

Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative, provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.

As of 2011 PHP does not have native support for Unicode or multibyte strings; Unicode support is under development for a future version of PHP and will allow strings as well as class-, method-, and function-names to contain non-ASCII characters.

PHP interpreters are available on both 32-bit and 64-bit operating systems, but on Microsoft Windows the only official distribution is a 32-bit implementation, requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. Experimental 64-bit versions of PHP 5.3.0 were briefly available for MS Windows, but have since been removed.

Licensing

PHP is free software released under the PHP License, which insists that:

                        4. Products derived from this software may not be called "PHP", nor may "PHP" appear in their name, without prior written permission from group@php.net. You may indicate that your software works in conjunction with PHP by saying "Foo for PHP" instead of calling it "PHP Foo" or "phpfoo"
                      

This restriction on use of the name PHP makes it incompatible with the GNU General Public License (GPL).

Release history

Beginning on June 28th, 2011, the PHP Group began following a timeline for when new versions of PHP will be released. Under this timeline, at least one release should occur every month. Every one year, a minor release should occur which can include new features. Every minor release should at least have 2 years of security and bug fixes, followed by at least 1 year of only security fixes, for a total of a 3 year release process for every minor release. No new features (unless small and self contained) will be introduced into a minor release during the 3 year release process.

Usage

PHP is a general-purpose scripting language that is especially suited to server-side web development where PHP generally runs on a web server. Any PHP code in a requested file is executed by the PHP runtime, usually to create dynamic web page content or dynamic images used on web sites or elsewhere. It can also be used for command-line scripting and client-side GUI applications. PHP can be deployed on most web servers, many operating systems and platforms, and can be used with many relational database management systems (RDBMS). 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.

PHP acts primarily as a filter, taking input from a file or stream containing text and/or PHP instructions and outputting another stream of data; most commonly the output will be HTML. Since PHP 4, the PHP parser compiles input to produce bytecode for processing by the Zend Engine, giving improved performance over its interpreter predecessor.

Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting, and it is similar to other server-side scripting languages that provide dynamic content from a web server to a client, such as Microsoft's ASP.NET, Sun Microsystems' JavaServer Pages, and mod_perl. PHP has also attracted the development of many frameworks that provide building blocks and a design structure to promote rapid application development (RAD). Some of these include CakePHP, Symfony, CodeIgniter, 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 is commonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer to Python or Perl or some combination of the three. Similar packages are also available for Windows and Mac OS X, then called WAMP and MAMP, with the first letter standing for the respective operating system.

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. PHP is used as the server-side programming language on 75% of all web servers. Web content management systems written in PHP include MediaWiki, Joomla, eZ Publish, WordPress, Drupal and Moodle. All websites created using these tools are written in PHP, including the user-facing portion of Wikipedia, Facebook, and Digg.

Security

Vulnerabilities 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). Recognizing that programmers make mistakes, some languages include taint checking to detect automatically the lack of input validation which induces many issues. Such a feature is being developed for PHP, but its inclusion in a release has been rejected several times in the past.

Hosting PHP applications on a server requires careful and constant attention to deal with these security risks. There are advanced protection patches such as Suhosin and Hardening-Patch, especially designed for web hosting environments.

PHPIDS adds security to any PHP application to defend against intrusions. PHPIDS detects Cross-site scripting (XSS), SQL injection, header injection, Directory traversal, Remote File Execution, Local File Inclusion, Denial of Service (DoS).

Syntax

Main article: PHP syntax and semantics

                        <!DOCTYPE html><html> <head> <meta charset="utf-8" /> <title>PHP Test</title> </head> <body>
                        
                          <?php
                        
                        
                          echo
                        
                        
                          'Hello World'
                        
                        
                          ;
                        
                        
                          /* echo("Hello World"); works as well, although echo is not a function, but a language construct. In some cases, such as when multiple parameters are passed to echo, parameters cannot be enclosed in parentheses. */
                        
                        
                          ?>
                        
                        </body></html>
                      

Hello world program in PHP code embedded within HTML code

The PHP interpreter