title: PHP instant messaging methods
body: <p>I want to make an IM so that user's can send instant messages to each others on the same page like a chat. Users can choose that who can see their messages. Its for task management . What is the best method that I should use for. I'm using php. Is php sockets  usefull for this? or Polling, Comet, php output buffer or javascript timer(timer is easy but not fast).</p>