PHP Programming Language

PHP (PHP: Hypertext Preprocessor) is a reflective programming language originally designed for producing dynamic Web pages. PHP is used mainly in server-side scripting, but can be used from a command line interface or in standalone graphical applications. Textual User Interfaces can also be created using ncurses.

Usage
PHP generally runs on a web server, taking PHP code as its input and creating Web pages as output, however it is also popular for command-line scripting and client-side GUI applications. PHP can be deployed on most web servers and on almost every OS platform free of charge. The PHP Group also provides the complete source code for users to build, customize and extend for their own use.

Server-side scripting
Originally designed to create dynamic web pages, PHP's principal focus is server-side scripting. While running the PHP parser with a web server and web browser, the PHP model can be compared to other server-side scripting languages such as Microsoft's ASP.NET system, Sun Microsystems' JavaServer Pages, mod_perl and the Ruby on Rails framework, as they all provide dynamic content to the client from a web server. To more directly compete with the "framework" approach taken by these systems, Zend is working on the Zend Framework - an emerging (as of June 2006) set of PHP building blocks and best practices; other PHP frameworks along the same lines include CakePHP, PRADO and Symfony.

The LAMP architecture has become popular in the Web industry as a way of deploying inexpensive, reliable, scalable, secure web applications. PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL. PHP can be used with a large number of relational database management systems, runs on all of the most popular web servers and is available for many different operating systems. This flexibility means that PHP has a wide installation base across the Internet; over 19 million Internet domains are currently hosted on servers with PHP installed.[8]

Examples of popular server-side PHP applications include phpBB, WordPress and MediaWiki.

Command-line scripting
PHP also provides a command line interface SAPI for developing shell and desktop applications, daemons, log parsing, or other system administration tasks. It is increasingly used on the command line for tasks that have traditionally been the domain of Perl, Python, awk, or shell scripting.

Client-side GUI applications
PHP provides bindings to GUI libraries such as GTK+ and text mode libraries like ncurses in order to facilitate development of a broader range of cross-platform GUI applications.