static function getConfigValue($heading, $key, $default = null)
    {
        // if we haven't read config file yet, do so.
        if (!isset(self::$_config)) {
            // read/stat INI once and only once per request
            self::$_config = parse_ini_file(CONFIG_FILE, true);
        }

        if (isset(self::$_config[$heading][$key])) {
            return self::$_config[$heading][$key];
        } elseif (isset($default)) {
            return $default;
        } else {
            return false;
        }
    }