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Posted by Michael Fesser on 12/19/07 18:23
..oO(macca)
>Facebook shows who's online by identifying which members have been
>active in the last five minutes.
>
>how? I'm not sure? maybe some kind of authentication and reading the
>apache access log? maybe some kind of database table?
You just have to keep track of active sessions. One way to do this in
PHP is to use your own session handler, which stores the session data
and a timestamp in a DB table (or just the timestamp in the DB and the
session data in flat files, whatever you like). Then you just have to
fetch all records that were updated in the past 5 minutes or something
like that.
But even this is just a wild guess and never really accurate. As said,
HTTP doesn't allow for accuracy here:
* user sends request
* user gets answer
* user is gone
It's always the same.
Micha
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