Google Storage - dynamically change ACL on single object (PHP)

Actually I've solved by using the Google_Service

  $client = new Google_Client();
  $client->setApplicationName('GoogleBuck/0.1');
  $client->useApplicationDefaultCredentials(); // app engine env
  $client->addScope('https://www.googleapis.com/auth/devstorage.full_control'); 
  $storage = new Google_Service_Storage($client);
  $acl = new Google_Service_Storage_ObjectAccessControl($client);
  $acl->setEntity('allUsers');
  $acl->setRole('READER');
  $acl->setBucket($bucketName);
  $acl->setObject($objectName);

To add

$response = $storage->objectAccessControls->insert($bucketName, $objectName, $acl);

To delete

$response = $storage->objectAccessControls->delete($bucketName, $objectName, 'allUsers');