php获取客户端IP

    function GetIP() { //获取IP       if ($_SERVER["HTTP_X_FORWARDED_FOR"])           $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];       else if ($_SERVER["HTTP_CLIENT_IP"])           $ip = $_SERVER["HTTP_CLIENT_IP"];       else if ($_SERVER["REMOTE_ADDR"])           $ip = $_SERVER["REMOTE_ADDR"];       else if (getenv("HTTP_X_FORWARDED_FOR"))           $ip = getenv("HTTP_X_FORWARDED_FOR");       else if (getenv("HTTP_CLIENT_IP"))           $ip = getenv("HTTP_CLIENT_IP");       else if (getenv("REMOTE_ADDR"))           $ip = getenv("REMOTE_ADDR");       else           $ip = "Unknown";       return $ip;    }