function get_ip(){

    //判断服务器是否允许$_SERVER

    if(isset($_SERVER)){

        if(isset($_SERVER[HTTP_X_FORWARDED_FOR])){

            $realip = $_SERVER[HTTP_X_FORWARDED_FOR];

        }elseif(isset($_SERVER[HTTP_CLIENT_IP])) {

            $realip = $_SERVER[HTTP_CLIENT_IP];

        }else{

            $realip = $_SERVER[REMOTE_ADDR];

        }

    }else{

        //不允许就使用getenv获取

        if(getenv("HTTP_X_FORWARDED_FOR")){

            $realip = getenv( "HTTP_X_FORWARDED_FOR");

        }elseif(getenv("HTTP_CLIENT_IP")) {

            $realip = getenv("HTTP_CLIENT_IP");

        }else{

            $realip = getenv("REMOTE_ADDR");

        }

    }

    return $realip;

}