// Include all Freenom classes
require_once 'vendor/autoload.php';

define('CREDENTIALS_PATH', '~/.credentials/{CREDENTIAL_FILENAME}');

$cli    = new Freenom_Client;
$client = $cli->getClient();

$service = new Freenom_Service($client);
$service->ping();
  
$register = $domain->shortenURL([
'url' => $details['prefix'].$details['domain']
]);
var_dump($register);

$domain      = new Freenom_Domain($client);
$listDomains = $domain->listDomains(['maxResults'=>100]);
var_dump($listDomains);

$ php {YOUR_FILE}.php