session_unset Free all session variables voidsession_unset The session_unset function frees all session variables currently registered. If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is used, use unset to unregister a session variable, i.e. unset ($_SESSION['varname']);. Do NOT unset the whole $_SESSION with unset($_SESSION) as this will disable the registering of session variables through the $_SESSION superglobal.