xml php curl请求的不支持的媒体类型

我得到的错误是：服务器无法为请求提供服务,因为媒体类型不受支持.

码：

$soapUrl = "http://clients.mindbodyonline.com/api/0_5/ClassService.asmx?WSDL";
// xml post structure

$xml_post_string = '<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Header/>
  <soapenv:Body>
     <GetClasses xmlns="http://clients.mindbodyonline.com/api/0_5/GetClasses">
        <Request>
           <SourceCredentials>
              <SourceName>{user}</SourceName>
              <Password>{pass}</Password>
              <SiteIDs>
                 <int>{id}</int>
              </SiteIDs>
           </SourceCredentials>
           <XMLDetail>Basic</XMLDetail>
           <PageSize>10</PageSize>
           <CurrentPageIndex>0</CurrentPageIndex>
           <SchedulingWindow>true</SchedulingWindow>
        </Request>
     </GetClasses>
  </soapenv:Body>
</soapenv:Envelope>
';

$headers = array(
    "Content-type: application/xml;charset=utf-8","Accept: application/xml","Cache-Control: no-cache","Pragma: no-cache","SOAPAction: http://clients.mindbodyonline.com/api/0_5/GetClasses","Content-length: ".strlen($xml_post_string),);

$url = $soapUrl;
$cookiePath = tempnam('/tmp','cookie');

$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_COOKIEJAR,$cookiePath);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch,CURLOPT_HTTPAUTH,CURLAUTH_ANY);
curl_setopt($ch,CURLOPT_SSL_VERIFYHOST,false);
curl_setopt($ch,CURLOPT_TIMEOUT,10);
curl_setopt($ch,CURLOPT_POST,CURLOPT_POSTFIELDS,$xml_post_string);
curl_setopt($ch,CURLOPT_HTTPHEADER,$headers);

// converting
$response = curl_exec($ch);
curl_close($ch);

echo $response;