public function get_param_validation() {
        switch ($this->vtype) {
            case self::IS_BOOLEAN:
                return PARAM_BOOL;
            case self::IS_INTEGER:
                return PARAM_INT;
            case self::IS_FILENAME:
                return PARAM_FILE;
            case self::IS_PATH:
                return PARAM_PATH;
            case self::IS_TEXT:
                return PARAM_TEXT;
        }
        return null;
    }