PHP logon / logoff design question

Question

I am thinking of implementing a small tracking system that will track users logon / logoff times and also track who is currently logged on. It all makes sense to me except for the tracking of when a user logs off. Its easy enough when a user clicks a "log off" button which calls a function that can update the database with the logoff time but what if the user just exits out of the browser. How can I create a function that will handle this event and I guess any other situations I have not thought of when a user exits a php application an informal way. Also, any links to online tutorials on this subject would be much appreciated.

Answer 1

you can use Javascript to call PHP function (via AJAX) on window unload event or just log user out after e.g. 30 minutes of inactivity automatically.

Answer 2

You won't be able to track when the user closes the browser or your page.

What I have attempted to ask about tracking user closing page: http://stackoverflow.com/questions/1619946/ajax-when-user-leaves-page-good-or-bad-practice-implementation

Apparently it's not that good to send data on the before_unload event.

Well what you can do is to consider users being logged off after inactivity for certain amount of time.

Each time when the users goes to a page, you store the timestamp. A user is said to be offline if the timestamp is more than 5 minutes old for example. You can store the timestamp into database or session.

Alternatively if you wish for it to be more accurate, you can call AJAX-ly every time interval (say 30 seconds) back to your server to prolong your activity timestamp.

Answer 3

The simplest solution is probably just to mark a user as "active" each time he does an action on your site (ie, each time a page is generated on the server) -- you already know how to do that.

And if a user has been marked as "active" a long time (ie, more than 5 minutes, for instance ; maybe more depending on the kind of content you have on your site) ago, you can consider he is not active anymore -- maybe not even on your site anymore, actually.

Of course, you have a couple of minutes of delay before detecting a user is not there anymore...

A possible complementary solution would be to use some kind of Ajax request done once every one or two minutes : this way, you have a shorter delay before detecting a user is not here anymore...

But, with this solution : you consider a user as active if he has a browser window/tab opened on your site -- even if he is not really using it (I always have lots of tabs opened in my firefox, some on websites I don't actually use for hours / days !)