PHP (officially "PHP: Hypertext Preprocessor") is a server-side HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly. It can also be used as a shell scripting language or even as a language to write windowed applications, in the form of PHP-GTK.

At the most basic level, PHP can do anything any other CGI program can do, such as collect form data, generate dynamic page content, or send and receive cookies.

Perhaps the strongest and most significant feature in PHP is its support for a wide range of databases. Writing a database-enabled web page is incredibly simple

PHP also has support for talking to other services using protocols such as IMAP, SNMP, NNTP, POP3, HTTP and countless others. You can also open raw network sockets and interact using other protocols.

Due to PHP's open-source nature, if there is something you can't currently do in PHP itself there is nothing stopping you from writing a PHP module or extension in C code to extend its functionality so that you can do what you want from within PHP itself. This is made possible through the well-documented API which is available to all.

PHP4 has two main parts to it:

• The Zend Engine is the part of the PHP package that keeps track of the requests, processes scripting files, and handles variables and resources. Its homepage can be found at http://www.zend.com/.
• PHP implements 90% of the functionality seen by the end user. It provides a wide range of modules such as MySQL, ODBC and XML support.