Magento，curl_exec功能不起作用

I am doing instagram login in magento, My curl_exec is not giving me the output here. I dont know what mistake i had done.

My code:

     private function _makeOAuthCall($apiData) {
$apiHost = self::API_OAUTH_TOKEN_URL;

$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_URL, $apiHost);
curl_setopt($ch, CURLOPT_POST, count($apiData));
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($apiData));
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Accept: application/json'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 echo "<pre>";
echo "get test::::";
print_r($ch);
$jsonData = curl_exec($ch);
echo "      gggg    ";
print_r($jsonData); die;
curl_close($ch);
return json_decode($jsonData);

}

Before curl_exe function, I am getting $ch value as Resource id #814, but the curl_exec() functions $jsondata variable return empty result.

Can anyone help me to fix this ? Thanks in advance.