php函数获取真实客户端IP地址

function getIPaddress(){
        $IPaddress='';
        if (isset($_SERVER)){
            if (isset($_SERVER["HTTP_X_FORWARDED_FOR"])){
                $IPaddress = $_SERVER["HTTP_X_FORWARDED_FOR"];
            } else if (isset($_SERVER["HTTP_CLIENT_IP"])) {
                $IPaddress = $_SERVER["HTTP_CLIENT_IP"];
            } else {
                $IPaddress = $_SERVER["REMOTE_ADDR"];
            }
        } else {
            if (getenv("HTTP_X_FORWARDED_FOR")){
                $IPaddress = getenv("HTTP_X_FORWARDED_FOR");
            } else if (getenv("HTTP_CLIENT_IP")) {
                $IPaddress = getenv("HTTP_CLIENT_IP");
            } else {
                $IPaddress = getenv("REMOTE_ADDR");
            }
        }
        return $IPaddress;
    }

使用直接
echo getIPaddress();