public function unique_if_diff($new, $params)
    {
        list($table, $column, $old) = explode(".", $params, 3);

        if ($new == $old) {
            return true;
        }

        if (!array_key_exists('unique_if_diff', $this->_error_messages)) {
            $this->set_message('unique_if_diff', lang('fv_unique_if_diff_field'));
        }

        $oDb = Factory::service('Database');
        $oDb->where($column . ' !=', $old);
        $oDb->where($column, $new);
        $oDb->limit(1);
        $q = $oDb->get($table);

        if ($q->row()) {
            return false;
        }

        return true;
    }