Differences between serialize() and what's in the session file

[TurboWaffle]

I thought that session data was converted to a string using serialize() but there seems to be some differences between the output of serialize() and the string that is in the session file.

<?
$foo = array('bar' => 'whoa');
$foo2 = array('ni'=>'geek');
print serialize($foo) . "\n" . serialize($foo2) . "\n";
$_SESSION['foo'] = $foo;
$_SESSION['um'] = $foo2;
print serialize($_SESSION) . "\n";
?>

a:1:{s:3:"bar";s:4:"whoa";}
a:1:{s:2:"ni";s:4:"geek";}
a:2:{s:3:"foo";a:1:{s:3:"bar";s:4:"whoa";}s:2:"um";a:1:{s:2:"ni";s:4:"geek";}}

While the file contains:

foo|a:1:{s:3:"bar";s:4:"whoa";}um|a:1:{s:2:"ni";s:4:"geek";}

Does anyone know why there is this discrepency? And how to get around it? PHP can't seem to unserialize() the string in the file, so I'm assuming something happens someplace else that turns it into a parseable string, but I'm not sure what. Thanks,
-Chris

[Weedpacket]

Yes, there is a difference: session data includes more information than just serialized values; it contains the session variable name "foo", followed by |, followed by the serialised value of $SESSION['foo'], and so on for all of the session variables. The example file parses as

foo   the following value is that of $_SESSION['foo']
|
a:1:{s:3:"bar";s:4:"whoa";} serialised value of $_SESSION['foo']
um   the following value is that of $_SESSION['um']
|
a:1:{s:2:"ni";s:4:"geek";}  serialised value of $_SESSION['um']