session_unregister() unregisters the global variable named name from the current session.
for PHP 4.0.6 or less) is used, use unset() to
unregister a session variable. Do not unset()
$_SESSION itself as this will disable the special
function of the
This function does not unset the corresponding global variable for name, it only prevents the variable from being saved as part of the session. You must call unset() to remove the corresponding global variable.