PHP is a widely-used scripting language intended for use in web pages to create dynamic content.

PHP runs on a web server, which interprets the PHP scripts behind the scenes and sends the results to the client. The client may not even know that a script was used to produce the contents of the webpage that they are viewing.

Although PHP is considered to be a simple language, it comes with an extensive list of features that allow it to be used in thousands of different ways to enhance websites and web applications. These uses include, but are by no means limited to:

Solving Math Problems
Displaying Current Dates & Times
Handling Form Data
Sending & Receiving Cookies
Collecting Information About Your Website's Visitors
Tools to Read From & Write Data to Databases
Creating/Modifying Images
Creating Shopping Carts
Interacting With a Secure 3rd Party to Pay For Online Merchandise

PHP is a free open source software already installed on many web servers today.

PHP stands for "PHP: Hypertext Preprocessor". It is a recursive acronym.