PHP - HyperText PreProcessor. It is a Open Source, server-side scripting language. Today PHP is one of the most popular and advanced languages. It was first designed by Rasmus Lerdorf in the year 1995, since then it has gained wide popularity and has attained a high position the world of programming by the contribution of it’s huge open source community.
PHP is used mainly in server-side scripting and Web Applications, but can be used from a command line interface or in standalone graphical applications. Unlike an ordinary HTML page, a PHP script is not sent directly to a client by the server; instead, it is parsed by the PHP binary or module, which is server-side installed. PHP code in a script can query databases, create images, read and write files, talk to remote servers - the possibilities are endless.
The output from PHP code is combined with the HTML in the script and the result sent to the user’s web-browser, therefore it can never tell the user whether the web-server uses PHP or not, because all the browser sees is HTML.
PHP’s support for Apache and MySQL further increases its popularity. Apache is now the most-used web-server in the world, and PHP can be compiled as an Apache module. MySQL is a powerful free SQL database, and PHP provides a comprehensive set of functions for working with it. The combination of Apache, MySQL and PHP is all but unbeatable.