PHP 获取ip地址

public function getIP()

    {

        if (getenv("HTTP_CLIENT_IP"))

            $ip = getenv("HTTP_CLIENT_IP");

        else if(getenv("HTTP_X_FORWARDED_FOR"))

            $ip = getenv("HTTP_X_FORWARDED_FOR");

        else if(getenv("REMOTE_ADDR"))

            $ip = getenv("REMOTE_ADDR");

        else

            $ip = "UNKNOWN";

        return $ip;

    }