PHP Authorization fail when post in google moment with plusapi

I think you have get authorization error because of following reason -

1. Not setting email id & project name using developer console link APIs & Auth->Consent Screen.
2. You are calling deprecated API $this->_CI->googleplus->item_scope->setId($post_data['gp_id']);. To Call this you have to use this class new Google_Service_Plus_ItemScope();
3. $this->_CI->googleplus->moment_body->setTarget($this->_CI->googleplus->item_scope); .To call this method you have to use this class new Google_Service_Plus_Moment();
4. I have setup demo code in git for you. Google-Plus-API-Codeigniter-Starter. You can use same code to start with. I have provided detailed instruction in git repository too.

5. You have to Register your application using Google Console Settings as below:

   • Go to Google Developer Console
   • Create Project
   • To Get Google+ API Access go to: APIs & Auth->APIs -> enable Google+ API
   • To Get client_id & client_secret go to: APIs & Auth->Credentials->Create new Client ID
   • To Get api_key go to: APIs & Auth->Credentials->Create New Key->Browser key
   • To Get application_name go to: APIs & Auth->Consent Screen
     1. Set Email Address
     2. Product Name

Note: Ensure you have get all the required access from google as mentioned in point 5

Conclustion: You are using Latest google-api-php-client client. And trying to call method in an older way. Hence its not working.