protected function diff($array1,$array2){
        if ($array1 === null) {
            if ($array2 === null) {
                return false; //indicate no diff
            }
            return $array2; //full array2 is new
        }
        if ($array2 === null) {
            //indicate that diff is there  (so return a true value) but everthing should be droped
            return 'null';
        }
        $diff = array_merge(array_diff_assoc($array1,$array2),array_diff_assoc($array2,$array1));
        return $diff;
    }