谷歌加上帖子无法在Google+上发布单个或多个图片或视频附件

Question

我在google plus帐户上发帖，但我只发帖子文字。如何发布图片或视频？

到目前为止，这是我的代码：

$service = new Google_Service_PlusDomains($client);
$activity = new Google_Service_PlusDomains_Activity(
   array(
      'access' => array(
          'items' => array(
              'type' => 'domain'
          ),
          'domainRestricted' => true
      ),
      'verb' => 'post',
      'object' => array(
          'originalContent' => "Post using Google API PHP Client Library! 1" ,
          'attachments' => ['image'=>array('url'=>$img_path)]
      ), 

   )
);

$newActivity = $service->activities->insert($user->id, $activity);    

var_dump($newActivity);