确定在PHP脚本是否连接到互联网？

<?phpfunction is_connected(){    $connected = @fsockopen("www.example.com", 80);        //website, port  (try 80 or 443)    if ($connected){        $is_conn = true; //action when connected        fclose($connected);    }else{        $is_conn = false; //action in connection failure    }    return $is_conn;}?>