private function generateRequestId()
    {
        static $pid = -1;
        static $addr = -1;

        if ($pid == -1) {
            $pid = getmypid();
        }

        if ($addr == -1) {
            if (array_key_exists('SERVER_ADDR', $_SERVER)) {
                $addr = ip2long($_SERVER['SERVER_ADDR']);
            } else {
                $addr = php_uname('n');
            }
        }

        return $addr . $pid . $_SERVER['REQUEST_TIME'] . mt_rand(0, 0xffff);
    }