Unable to retrieve an access token for Google's API using google-api-php-client

Question

I'm trying to receive an access token from the Google API:

$client = new Google_Client();        
$client->setAuthConfig('service-account.json');        
$client->setScopes('https://www.googleapis.com/auth/bigquery');        
$client->setSubject($user_to_impersonate);    
var_dump($client->getAccessToken());    

I already tried with GOOGLE_APPLICATION_CREDENTIALS but that returns null , too:

$client = new Google_Client();       
putenv('GOOGLE_APPLICATION_CREDENTIALS=service-account.json');        
$client->useApplicationDefaultCredentials();        
$client->setScopes('https://www.googleapis.com/auth/bigquery');        
$client->setSubject($user_to_impersonate);        

Answer 1

All right... I saw what is happening... My json service account file was deprecated. I nedded to download it again, so it came with more vars on json file... The deprecated one has only 3 fields...