Sessions and expiring cookies

[Derek Fountain]

I set my session parameter so the session is a few minutes long, and if the
user goes inactive for that period the session expires. Two questions:

1) What mechanism actually expires the session? That is, what says "hang on,
the time limit has passed, so that's no longer valid"? It can't be the
browser, since that might be subverted or buggy. So does a browser send an
expired cookie value anyway and trust the website to spot it has expired?

2) How do I tell in my PHP that a session has expired? My code has a
start_session() at the top, and uses of $_SESSION[xxx] underneath, but
somewhere I should be checking that the session hasn't expired, shouldn't
I? Or maybe start_session() does that for me somehow?

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[R. Rajesh Jeba Anbiah]

Derek Fountain wrote:

I set my session parameter so the session is a few minutes long, and if the user goes inactive for that period the session expires. Two questions:
1) What mechanism actually expires the session?
session.gc_maxl ifetime <http://in2.php.net/session>
2) How do I tell in my PHP that a session has expired?

Check if the set/expected variable is in the $_SESSION array.

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