CURL POST，版本为PHP 5.3.10和libcurl 7.22

Question

使用此代码

        $response = null;

    // CURL configuration
    $ch = curl_init($url);

    // User password to GoMobi API
    curl_setopt($ch, CURLOPT_USERPWD, sprintf("%s:%s", self::GO_MOBI_USER, self::GO_MOBI_PASS));

    // Set http method
    switch ($httpMethod)
    {
        case self::HTTP_METHOD_GET:
            curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
            break;
        case self::HTTP_METHOD_PUT:
            curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT');
            break;
        case self::HTTP_METHOD_DELETE:
            curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'DELETE');
            break;
        case self::HTTP_METHOD_POST:
        default:
            curl_setopt($ch, CURLOPT_POST, 1);                
            break;
    }

    // XML data to api
    if (!is_null($xml))
    {
        curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
    }

    // More CURL options
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

    // Exec
    $output = curl_exec($ch);
    $info = curl_getinfo($ch);
    curl_close($ch);

我已经调用了这个URL：https://api-sandbox.instantmobilizer.com/v1/subscription/c1652b83ffb484d0/suspend以及之前版本的PHP 5.3.2和libcurl 7.19.7，它没问题，但是PHP 5.3.10和libcurl 7.22失败了。返回的错误是：«400 Bad request。您的浏览器发送了无效请求。»

由于