PHP/MySQL
Database Development
PHP is a widely used programming language for the web. It can be used to check and send user input from forms, run scripts, create web pages and communicate with databases. MySQL is a database format which is often included as part of a site hosting package but does not have a user-friendly interface. The two can be combined to create database systems with login and registration systems, custom screens with buttons and menus, one-click reports, etc, where MySQL is used to store the information and PHP to create the user interface.
There are several open source (free) PHP/MySQL systems available, such as WordPress and Drupal, which are used to create websites. They allow someone to add or edit web pages without needing to know how to write HTML or program in PHP. The database stores information such as user ids and passwords and the actual text or images for the web pages. The PHP code creates screens for text entry, image uploading, etc. These packages also have a wide range of user-contributed modules, such as website designs (themes) or code to do special things (create calendars, make forums, etc.) which can be combined with the basic package to customize a website, add features, or create a particular look and feel.
PHP can also be used without a database, to create menus, validate forms, run slideshows, etc. This site uses PHP to generate the menus in the upper right, based on what section of the website you are in. It does this without a database, using the current site section to pick a folder on the server and s generate links to the files within.