GoToWebinar API Support

Hello, 
we have create a sample php page with this code

$clientID = 'CLIENT ID DEL CLIENTE';
$response_uri = 'response_uri';
$curl = curl_init();
curl_setopt_array($curl, array(
  CURLOPT_URL => 'https://authentication.logmeininc.com/oauth/authorize?client_id='.$clientID.'&response_type=code&response_uri='.$response_uri,
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => true,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => 'GET',
));
$response = curl_exec($curl);
curl_close($curl);
echo $response;

If he calls it he sees the behavior we get these page result:

if i call the url https://authentication.logmeininc.com/oauth/authorize?client_id=clientID&response_type=code&response_uri=response_uri 

directly from browser i see the corrected screen

Can you help me?

Thanks
regards.
B.