PhpWiki is a WikiWikiWeb clone written in PHP. A Wiki is a Web site where anyone can edit or create the pages through the Web browser, with no authentication. PhpWiki works right out of the box with zero configuration, and comes with a set of default pages. It's useful for collaborating on documentation on a project, having freeform discussions, and easy editing and searching.
ARSC Really Simple Chat is a Web chat system that uses PHP and MySQL. It works with every browser in existence, even text-based ones, and it uses the server push technique or, if possible, its own socket server. It is very simple to install and use ARSC. It includes some important features, such as operators, kick-ing, whispering, and more. Multiple rooms and different languages are available. To run ARSC on your site, you need a Web server that understands PHP, and can connect to a MySQL database.
MAHC is a complex PHP system that installs easily and allows people to chat using only HTML. Features include multiple rooms, private chat, user colored chat text, games (checkers, chess, hangman, tictactoe, dicezee, crossword), private chat, a "weak" AI chat, Inter-chat messaging, selectable MIDI music, and 3D graphical smilies. The Web server requirements are currently only PHP4 and a crontab facility. The current version is stable, but lacks in documentation.