Yeah... I think it's safe to say that something like this can't be done in PHP. I really can't think of any way PHP would be directly involved with such a chatroom.
I mean, if you wanted to accompany the audio chat with a text-only chat lobby, I could see that being done in PHP/AJAX/etc., but other than that... yeah, I don't think so. As such, I think this thread is destined for the ClientSide Technologies forum.