PHP is the open source nemesis of ASP. A completely free and viable option for writing dynamic web pages. Team it up with Apache and MySQL and you are AMPed up for success. PHP is a server side object oriented language. It is often refereed to as a scripting language but it has evolved to much more than simple scripts.
Type something into the address bar and you make an HTTP request. Instead of a normal HTML page, php code can be inserted and parsed before the response is sent to the clients browser. This lets you manipulate what the client sees instead of a boring static page you can enrich it with dynamic content.
If you are a developer, the first two useful tasks you will probably complete is the ability to process html forms and query a database. Do all PHP developers a favor and validate your form input. This is one of the many keys to a secure application. PHP gets a bad rap because it is an easy tool to use so it attracts a larger proportion of amateur developers.
Not much of a developer, use php by accessing the enormous library of tools such as WordPress, phpBB, phpMyAdmin, drupal and many more. In a LAMP scenario, setup is as simple as “apt-get”. Use this in linux to install new software on your free server.