public static function getObjectUsers($action, $objectType, $objectId)
    {
        global $PPHP;
        $db = $PPHP['db'];

        $out = $db->selectList(
            "
            SELECT userId FROM acl_users
            WHERE action=? AND objectType=? AND objectId=?
            ORDER BY userId ASC
            ",
            array(
                $action,
                $objectType,
                $objectId
            )
        );
        return (is_array($out) ? $out : array());
    }