Resource id #2 réponse de curl de php

Je suis en train d'interpréter cette ligne de commande dans curl de php

commande curl:

curl https://api.sandbox.paypal.com/v1/oauth2/token \
 -H "Accept: application/json" \
 -H "Accept-Language: en_US" \
 -u "{clientId}:{secret}" \
 -d "grant_type=client_credentials"

Voici mon curl de php code:

$url = 'https://api.sandbox.paypal.com/v1/oauth2/token';
$info = array(
        'grant_type' =>'client_credentials'
);
 $post_field_string = http_build_query($info, '', '&');

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(                                                                          
    'Content-Type: application/json',                                                                         
    'Accept-Language: en_US')
); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_USERPWD,'AQHeHhDPIpAoxWaNkXOwCNFV4cZUobhqDa_4qHPKh0iDrSd6rLaxIknT-lmgwd:EJHLmhBMT9dB48kou4V0jyJzaq-CqUlY0zS6QKsxOZKI15hZHZjTfoSV7MO8we');
curl_setopt($ch, CURLOPT_POSTFIELDS,   $post_field_string );
 curl_setopt($ch,CURLOPT_POST,1);
curl_setopt($ch, CURLOPT_HEADER,1);   
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");    

$exec = curl_exec($ch);
curl_exec($ch);

curl_close($ch);

Et j'obtiens ce résultat:

Resource id #2

Je suis nouveau sur curl mais je suis en train de l'étudier. Est-ce le bon code dans mon curl de php?

J'attends cet exemple de réponse de curl:

{
  "scope": "https://api.paypal.com/v1/payments/.* https://api.paypal.com/v1/vault/credit-card https://api.paypal.com/v1/vault/credit-card/.*",
  "access_token": "EEwJ6tF9x5WCIZDYzyZGaz6Khbw7raYRIBV_WxVvgmsG",
  "token_type": "Bearer",
  "app_id": "APP-6XR95014BA15863X",
  "expires_in": 28800
}

OriginalL'auteur user3391620 | 2014-06-04