curl namelookup_time of 10 seconds

当在PHP中执行对纯文本网页(http://whatismyip.org/)的基本curl请求时，需要超过10秒才能响应。

查看curl的信息后，它告诉我namelookup_time是10秒。当从命令行(终端)执行curl时，我可以看到完全相同的结果。

为什么要花这么长时间来查找，从我所读到的，它很可能与PHP文件托管的服务器/我的计算机有关。

下面是我的代码:

$ch = curl_init();  
curl_setopt( $ch, CURLOPT_URL, "whatismyip.org");
curl_exec( $ch );
$ci = curl_getinfo($ch);
print_r($ci);

信息如下:

[url] => HTTP://whatismyip.org 
[content_type] => text/plain 
[http_code] => 200 
[header_size] => 45 
[request_size] => 53 
[filetime] => -1 
[ssl_verify_result] => 0 
[redirect_count] => 0 
[total_time] => 10.549943 
[namelookup_time] => 10.100938 
[connect_time] => 10.300077 
[pretransfer_time] => 10.300079 
[size_upload] => 0 
[size_download] => 14 
[speed_download] => 1 
[speed_upload] => 0 
[download_content_length] => -1 
[upload_content_length] => 0 
[starttransfer_time] => 10.549919 
[redirect_time] => 0 
[certinfo] => Array ( )