Switching sessions mid-stream

I have an app that stores the user's IP and useragent with the session... then also stores the session ID in the database.

Every time a page is accessed, I check the current session against the one in the DB. If they're differerent, voila, I can tell the account is logged in from two different computers at the same time.

What I'm trying to do now is switch over to the canned session and fetch the old IP and useragent so I can log them. My code is as follows:


$oldsess = (fetched from user record in db)
$newsess = session_id();

if ($oldsess != $newsess) {

      session_id($oldsess);            // switch to the one we found in the db
      session_start();
      $oldIP = $_SESSION['ip'];
      $oldUserAgent = $_SESSION['useragent'];
      
      session_id($newsess);            // switch back to the current one
      session_start();
      $newIP = $_SESSION['ip'];
      $newUserAgent = $_SESSION['useragent'];

The problem is that it's not really 'switching' sessions when I try to go to the old one-- at the end of the code above, $oldIP == $newIP and $oldUserAgent == $newUserAgent.

Why is this failing? Does switching sessions require a page refresh (so http headers are sent), or something like that?

E

p.s. I'm trying to avoid storing the IP address in the db, though that would be a different way to solve this.
pnoericAsked:
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jkna_gunnConnect With a Mentor Commented:
i had never used session_id before so checked on php.net, and it says that it needs to be called before session_start
but since you are calling session_id and session_start twice then i dont think it would work. as the second time you call session_id the session has already started. try session_destroy before using session_id the second time.
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jkna_gunnCommented:
does session_id not need to be called before session_start??, so when you try to switch back it fails.
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pnoericAuthor Commented:
eh? not sure I follow. session_id sets the session, then session_start "kicks it into place." or so I believe that's how it works. or are you saying try it without the session_start after switching it with the _id?
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pnoericAuthor Commented:
Ugh. I tried it-- then I get "Session object destruction failed" on the line with session_destroy

Very, very strange. Any other ideas? I can't tell if the problem is that sessions are buggy or the documentation is just really fuzzy.

best
Eric
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pnoericAuthor Commented:
Never was able to really get this working :-( Sesssions seem to either be broken in PHP or not documented well enough that I could figure out how to switch 'em in mid-stream. I ended up just storing the IP address and running with that.

I'm crediting jkna_gunn the points since s/he tried to help me out :-)

best
Eric
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