In-Site Instant Messaging-Framework?

Is there any instant messaging framework or service that enables in-site chatting like the Facebook chat-bar or 开发者_JAVA技巧the Meebo bar?

I think you should read about COMET. For making your own instant messaging system.

You can find more information on wikipedia:

http://en.wikipedia.org/wiki/Comet_%28programming%29

There seems to be a solution now named CometChat, which is a commercial product.

http://www.cometchat.com/

As already mentioned this could be implemented via a technique called Comet. (The term was coined by Alex Russell in a blog entry.) But PHP does not seem to be very well suited for this technique as already discussed on StackOverflow:

• Using comet with PHP?
• How to implement a chat room using Jquery/PHP?
• solution for COMET and PHP

You should have a look at these threads because they also provide further explanations as well as hints for solutions or alternativ implementations.