Re: Handling competing edits in a wiki engine?

Murray @ PlanetThoughtful wrote: > > Out of curiosity, does anyone know if it's possible to tell whether an > individual session is still alive from PHP? I don't mean from within > code being run for a particular user, but in code that, for example, > might be executed by a cron job, which would examine a table in which > session ids have been recorded automatically for each visitor, and > determining which of those sessions are still theoretically alive? I > suspect this isn't possible, but I've also learned to never > underestimate the ingenuity of those faced with things that aren't > possible. > [Ok, I AM an AJAX fan] The problem with "normal" session management is that session data (timestamp etc.) gets updated only when and if the user does something: therefore, if he is reading an article and he doesn't click anywhere for 10 minutes, he still is on your site, but you "lose" him. An alternative approach is the AJAX [1] one: you set up a JavaScript 'setInterval' and call an "AJAX" function that makes a query to the PHP script that updates the session (with the current timestamp, user_id, whatever...) Ok, I don't know if this makes much sense, but you end up with a script that gets executed (without user interaction) every 'n' microseconds, so your session data is always up to date (at maximum, with a delay of 'n' * 2 microseconds). The bad side of this is that you have a script that gets executed quite often for every user visiting your pages: but, if you keep it minimal (a couple of queries) the overhead isn't that much and you get a *near-to-real* number of open sessions. I hope I made some sense: in any case feel free to ask, I just developed something like this for a web site I'm working on (but we're still in alpha), so if you want to see it in action, lemme know. Ciao! Silvio [1] http://en.wikipedia.org/wiki/AJAX