title: AJAX chat without periodic refresh?
body: <p>I'm about to write a ajax based Chat. 
  What is the best way to refresh the chat box? I know there are few possibilitys but which is best suited for a Chat? </p>
  
  <p>Additional:
  Is it possible just to reload the unread text? If someone writes an text it isn't nessecarry to refresh the whole content.The new message would be enough. But can it be done with ajax and php? I have no idea how it could be done. So I would be thankfull for even a tipp ...
  Thanks!</p>