public function getServerOs()
    {
        if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
            return self::OS_WINDOWS;
        } else {
            if (strtoupper(substr(PHP_OS, 0, 3)) === 'MAC') {
                return self::OS_MAC;
            } else {
                return self::OS_LINUX;
            }
        }
    }