php5-fpm cURL返回200但JSON数据为空

Question

I'm trying to make a REST call with cURL and the response is showing 200 while the JSON data is empty e.g., {}. When I try the same call with a REST client the response contains the correct data:

{
    "acceptLanguage": "en-US,en;q=0.8,fr-CA;q=0.6,fr;q=0.4,es;q=0.2,ar;q=0.2,de;q=0.2"
}

Here is my code:

$ch = curl_init();
// set URL and other appropriate options
$url = "http://my/api/service?_=1392236562419";
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt ($ch, CURLOPT_HTTPHEADER, array ('Content-Type: application/json'));
curl_setopt ($ch, CURLOPT_RETURNTRANSFER , True);
// grab URL and pass it to the browser
$response = curl_exec($ch);
// close cURL resource, and free up system resources
curl_close($ch);
print_r($response);

Do I need to escape quotes or something, or is my cURL request missing something?

Thanks.