PHP, which stands for "Hypertext Preprocessor", is a server-side, HTML embedded scripting language used to create dynamic Web pages. Much of its syntax is borrowed from C, Java and Perl with some unique features thrown in. The goal of the language is to allow Web developers to write dynamically generated pages quickly. In an HTML page, PHP code is enclosed within special PHP tags. When a visitor opens the page, the server processes the PHP code and then sends the output (not the PHP code itself) to the visitor's browser. It means that, unlike JavaScript, you don't have to worry that someone can steal your PHP script. PHP offers excellent connectivity to many databases including MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, and Generic ODBC. The popular PHP-MySQL combination (both are open-source products) is available on almost every UNIX host. Being web-oriented, PHP also contains all the functions to do things on the Internet - connecting to remote servers, checking email via POP3 or IMAP, url encoding, setting cookies, redirecting, etc. PHP reached wide-spread popularity with version 4, released in 2000. In 2004 PHP 5 was debuted, and it is now considered one the top languages used for server-side scripting. No doubt much of its popularity is due to its relative ease to learn, and its notorious looseness. Arrays and variables in PHP are able to hold any type of object, variables need not be declared, and the syntax is remarkably simple. Unlike many languages, such as C# or Perl, which have primarily a following of more generalist programmers, many PHP programmers know no other language. This occasionally causes it to be dismissed as a lesser language, but its growing popularity and the many robust and efficient sites built using it as a structure seem to dispel this myth. PHP has occasionally been criticized for what are viewed by some as security flaws, in comparison to languages such as ASP. A lack of easily understandable error messages, a sometimes overly robust configuration file, and an obviously incomplete set of built-in functions are also pointed to as areas which could use marked improvement. For more tutorials on PHP, visit the link below: http://www.php.net/
Great info. If your really interested in PHP download a WAMP server or a LAMP (depending on your OS), that way you can play around with PHP and its functions in MySQL database and in web development in general.