Displaying members online

[john9292]

To display members online on my website I use a database entry called "login" which is updated whenever the user logs in or out.

All of the users with "login" = yes are displayed on the site and vice versa.

The problem is - what if a user logs in, the database is updated, and then they close their browser, the session expires and then the database is not updated but they are actually logged out i.e. logged out but not according to DB.

Is there a way of updating the DB when the session ends, other techniques would be appreciated to.

Thanks anyone

[zabmilenko]

I use two ways of doing this:

1) Set up a routine task through cron or task scheduler that cleans old stale sessions every 30-60 minutes. (Some sites like 3-5 minutes, but I don't usually need that type of monitoring).

2) Add a generalized cleanup to the logout page (or any page that you want, for that matter), so people who access that page will also clean up sessions that are stale.

Some people may disagree with number 2, but my logic is that if they are logging out, then they probably won't notice or really care about the 10th-of-a-second query that runs along with their logout script. If lots of people log out, it will be even faster since only a few rows will be cleared at a time.

Your query could be something like:

"delete from sessions where timeout < $time"

The downside is, you have to also update the timeout in the database, per session, each time they click a page.

[john9292]

Ok I think ill go with the second idea.

So if you click a page the timeout resets to say 20min (20mins till session destroyed by the query). Is that correct?

Or if the user closes the browser without logging out the session will end in 20min anyway.

So is $time the actual time or some kind of counter.

Cheers

[john9292]

I copied this from another post on the forum although I cannot get it to work. I set the session expire to a short time so I could test if it is working.

Please give me any hints as to why this does not work.

Cheers

	$query = "UPDATE accounts SET timeout = UNIX_TIMESTAMP() WHERE alias = '".$_SESSION['alias']."' LIMIT 1"
		or die("MySQL Error: ".mysql_error());

$query = "UPDATE accounts SET login = 'no' WHERE timeout > (UNIX_TIMESTAMP() - 30)"
	or die("MySQL Error: ".mysql_error());

[zabmilenko]

Well, the "timeout" should be in the future when you set it:

// page request:
timeout += 20 mins

// check
if (time > timeout) { no good }

// cleanup
delete all which time > timeout