curl 보낼 때 param을 넣어 보냈는데 response에서 필요한 항목이 없다고 나와요.

function curl($url, $is_post = false, $data = array(), $custom_header = NULL)
{
 //승인 요청을 보내는 함수입니다.
 $ch = curl_init ();
 curl_setopt ($ch, CURLOPT_URL, $url);
 curl_setopt ($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
 curl_setopt ($ch, CURLOPT_SSLVERSION, 1);
 curl_setopt ($ch, CURLOPT_POST, $is_post);
 if ($is_post) {
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
  curl_setopt ($ch, CURLOPT_POSTFIELDS, $data);
 }

 curl_setopt ($ch, CURLOPT_TIMEOUT, 300);
 curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt ($ch, CURLOPT_FOLLOWLOCATION, 1);
// curl_setopt ($ch, CURLOPT_HEADER, true);
// curl_setopt ($ch, CURLINFO_HEADER_OUT, true);

 if ($custom_header) {
  curl_setopt ($ch, CURLOPT_HTTPHEADER, $custom_header);
 }
 $result[0] = curl_exec ($ch);

 curl_close ($ch);
 return $result[0];
}

$reqParams = array(
                'grant_type' => 'refresh_token'
            , 'refresh_token' => $code_to_update['refresh_token']
            );
            $header = array(
                'Content-Type: application/json'
            , 'Authorization: Basic key val' 
            );

            $res = curl('url', true, $reqParams, $header);
            print_r($res);