PHP/AJAX Chat - The Facebook Version

[kratsg]

So, my basic question would be.. "Have you seen the new chat Facebook has released?"

 

It uses simple PHP/AJAX obviously. What I can't seem to figure out is how to get my chat to be as efficient as theirs. (And yes, it's amazing, their average time is like 200 milliseconds for a heck of a lot of data to read through/transmit). It's also interesting to note that they're not sending any messages via AJAX (if you look at the POST calls to the php file, nothing you type is actually being transmitted via that method).

 

Any ideas on how they did theirs?