PHP
PHP is a server-side scripting language that web designers use to create dynamic web sites. The scripts use a combination of PHP and HTML code. When somebody opens the web page, they start the process of sending various PHP commands to the server and then the results are sent back to the browser. PHP scripts run on Windows NT and many Unix and LINUX versions and are known for returning results quickly yet keeping the server's memory use low.
In addition to manipulating the content of your pages, PHP can also send HTTP headers. You can set cookies, manage authentication, and redirect users. It offers excellent connectivity to many databases (and ODBC), and integration with various external libraries that let you do everything from generating PDF documents to parsing XML.
PHP goes right into your Web pages, so there's no need for a special development environment or IDE. (You can also configure PHP to use ASP-style tags.) The PHP engine processes everything between those tags.
PHP's language syntax is similar to C's and Perl's. You don't have to declare variables before you use them, and it's easy to create arrays and hashes (associative arrays). PHP even has some rudimentary object-oriented features, providing a helpful way to organize and encapsulate your code.
Although PHP runs fastest embedded in Apache, there are instructions on the PHP Web site for seamless setup with Microsoft IIS and Netscape Enterprise Server. If you don't already have a copy of PHP, you can download it at the official Web site. You'll also find a manual that documents all of PHP's functions and features.