public function unique(array $arr1, array $arr2)
    {
        Deprecated::method(3.2);

        $merged = array_unique(array_merge($arr1, $arr2), SORT_REGULAR);
        $compiled = [];

        foreach ($merged as $key => $val) {
            if (is_array($val) && array_values($val) === $val) {
                $compiled[$key] = $val;
            } else {
                $compiled[$val] = $val;
            }
        }

        return $compiled;
    }