PHP Manual Function Reference Session Extensions Sessions Session Functions session_unset session_unregister session_write_close session_unset (PHP 4, PHP 5)session_unset — Free all session variables Description void session_unset ( void ) The session_unset() function frees all session variables currently registered. Return Values No value is returned. Notes Note: 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']);. Caution Do NOT unset the whole $_SESSION with unset($_SESSION) as this will disable the registering of session variables through the $_SESSION superglobal.