private function IsFieldLocked($field)
    {
        if (!is_array($this->locked_fields)) {
            return false;
        }
        $locked_tables = array_keys($this->locked_fields);
        $locked_fields = array_values($this->locked_fields);
        $_locked_fields = array();

        foreach ($locked_fields as $locked_field) {
            if (is_array($locked_field)) {
                foreach ($locked_field as $_locked_field) {
                    $_locked_fields[] = $_locked_field;
                }
            } else {
                $_locked_fields[] = $locked_field;
            }
        }

        if (in_array($this->table, $locked_tables) and in_array($field, $_locked_fields)) {
            return true;
        }

        return false;
    }