Opensource Chat Application?

Question

I have a prosperity application written in-house in PHP for collaboration (Basecamp knock off). We're looking for a way to add IM chat (facebook or gmail style chat), is there a opensource solution we could use with great documentation and a easy to use API?

Platform: Linux, PHP 5, MySQL, SmartyPHP and Zend Framework.

Answer 1

Maybe you could use Chris Coyier's Chat Room.
http://css-tricks.com/chat2/

Another might be Ajax IM
http://ajaxim.com/

Answer 2

Search for Jabber. It's an open standard based IM protocol. There are several open source implementations which you can use. Also, there are several PHP Client API's which you probably can suit to your needs.