function get_var_names($file_name, $section = NULL)
	{
		if (empty($file_name)) {
			$this->_trigger_error_msg('Empty config file name');
			return;
		} else if (!isset($this->_config_data[$file_name])) {
			$this->_trigger_error_msg("Unknown config file '$file_name'");
			return;
		}

		if (empty($section))
		return array_keys($this->_config_data[$file_name]["vars"]);
		else
		return array_keys($this->_config_data[$file_name]["sections"][$section]["vars"]);
	}