Slub is a PHP bot I made. It is based upon an IRC class I also wrote which features:

• Using socket_select to create a non-blocking environment, allowing any number of bots to be run from one script
• Auto-reconnect on connection closed
• Handling of multiple bots to do one job
• Ability to change nick if it's in use automatically
• ...and then change back as soon as it's free
• Auto-joining channels after a disconnect
• Ability to run PHP code automatically on each connect
• Settings for reconnecting rates if a connection failed
• Ability to use modules, for coding
• Functions to list all users in a channel, along with admin levels (+vhoaq)
• Functions to get the current topic of a channel
• Ability to whois users to get more info about them (although best to keep it disabled)
• Contains a function to strip mIRC colour codes from a message
• Modules also have callbacks, for when users join, part, get kicked, change nick, etc., etc., etc.

Using the modules, you can program this IRC bot to do just about anything. The class is just a very useful backbone.

This bot is currently being used by Xendot.com for use in generating IRC stats.