cURL 有时有效，有时无效

这就是我手头的情况。我从 php 发出这样的卷曲请求：

$ch = curl_init ( $url );
curl_setopt ( $ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Firefox/31.0' );
curl_setopt ( $ch, CURLOPT_HEADER, true );
curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, true );
curl_setopt ( $ch, CURLOPT_FOLLOWLOCATION, true );
curl_setopt ( $ch, CURLOPT_SSL_VERIFYPEER, false );
curl_setopt ( $ch, CURLOPT_CONNECTTIMEOUT, 10 );
curl_setopt ( $ch, CURLOPT_TIMEOUT, 10 );
curl_setopt ( $ch, CURLOPT_VERBOSE, true );
$header = curl_exec ( $ch );
curl_close ( $ch );

网址是重定向的短网址。有趣的是，这只发生在 ift.tt 的短网址上。有时它会得到响应，有时它只是在请求时挂起。这是它挂起时的样子：

* About to connect() to ift.tt port 80 (#0)
*   Trying 69.58.188.49... * connected
* Connected to ift.tt (69.58.188.49) port 80 (#0)
> GET /1K0Hs73 HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Firefox/31.0
Host: ift.tt
Accept: */*

关于它为什么这样做的任何想法？几天前它工作得很好。我什么也没改变。