Description:
------------
Session_regenerate_id(true) leaves a bunch of new sessions behind when stress-testing by doing a continue page refresh (F5 in IE/Windows).




Reproduce code:
---------------
<?php
session_start();

$old_sessionid = session_id();

session_regenerate_id(true);

$new_sessionid = session_id();

echo "Old Session: $old_sessionid<br />";
echo "New Session: $new_sessionid<br />";

echo "Please look for the amount of newly created sessions in " . session_save_path();

?>

Navigate to this file with your browser and hold F5 continuously for 5 seconds, triggering multiple refreshes after each other.


Expected result:
----------------
Only 1 session should be in the session_save_path (the newly generated session only, the old ones should have been deleted).


Actual result:
--------------
Multiple sessions were created, it seems that the PHP-engine didn't have the time(?) to delete the old sessions.