I'm aiming to track all people on my site at one time, registered users is no problem as I can just use their unique id and a time() in a db, and only check users online <15mins ago. For guests though, I need a way of tracking them that would assign them each a unique id. Is it possible to get a session id number and store that in a table along with time of last action? And more importantly is this a good way to go about what I want?!