PHP (Hypertext Preprocessor) a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. You can easily jump to PHP code in your HTLM page by writing the PHP code in between special start and end tags.
PHP is a server side script that means that PHP code is executed at server side. PHP can be used on all major operating systems, including Linux, many Unix variants (including HP-UX, Solaris and OpenBSD), Microsoft Windows, Mac OS X, RISC OS, and probably others. There are many other features and benefits PHP can offer.