PHP stands for PHP: Hypertext Preprocessor, which means that it is a powerful tool for creating dynamic and interactive webpages. It is widely used, free and efficient (alternative to Microsoft's ASP).
What Is A PHP File?
It is a file that contains text, HTML tags and scripts that can be returned to the browser as plain HTML.
What Is MySQL?
It is a database server that is ideal for small and large applications and is free to download and use.
PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform
PHP runs on different platforms including windows,Linux and Unix etc. It is also compatible with almost all the servers (Apache,IIS etc).