Full form of PHP is Hypertext Preprocessor
PHP is the most popular and widely used server side scripting language for web development. It is used to make the Dynamic pages in websites.
Rasmus Lerdorf was the creator of PHP in 1995.
PHP codes are embedding in HTML source codes for making the page dynamic. PHP can deal with most of the requirements in web development like Database, File handling, String operations, Arrays, Graphics, File Uploads, Data processing etc.
PHP can be used in any operating system with a web server Supports PHP. Apache web server is one of the popular web server dealing with PHP + MySQL. Moreover PHP is absolutely free to use.