accessToken = GoogleAuthUtil.getToken(
                        AuthenticatorActivity.this,
                        Plus.AccountApi.getAccountName(Common.mGoogleApiClient),
                        "oauth2:https://www.googleapis.com/auth/plus.me https://www.googleapis.com/auth/plus.login email"
                );

https://www.googleapis.com/oauth2/v1/tokeninfo?access_token='.$_POST['google_access_token']

if (!isset($_POST['google_access_token'])) {
        throw new Exception('missing google_access_token');
    }


    $client = new Google_Client();
    $client->setApplicationName("GiverHub");

    $client->setClientId($this->config->item('google_client_id'));
    $client->setClientSecret($this->config->item('google_client_secret'));

    $client->setDeveloperKey($this->config->item('google_developer_key'));
    $client->setRedirectUri($this->config->item('google_redirect_uri'));

    $client->setScopes([
        'https://www.googleapis.com/auth/plus.login',
        'https://www.googleapis.com/auth/plus.me',
        'email',
    ]);



    try {
        $client->authenticate($_POST['google_access_token']);  // if i remove this the rest of the code below works!  ...
        $reqUrl = 'https://www.googleapis.com/oauth2/v1/tokeninfo?access_token='.$_POST['google_access_token'];
        $req = new Google_Http_Request($reqUrl);

        $io = $client->getIo();
        $response  = $io->executeRequest($req);


        $response = $response[0];

        $response = json_decode($response, true);
        if ($response === null) {
            throw new Exception('Failed to check token. response null');
        }

        if ($response['issued_to'] !== '466530377541-s7cfm34jpf818gbr0547pndpq9songkg.apps.googleusercontent.com') {
            throw new Exception('Invalid access token. issued to wrong client id: '. print_r($response, true));
        }

        if (!isset($response['user_id'])) {
            throw new Exception('Missing user_id');
        }

        if (!isset($response['email'])) {
            throw new Exception('Missing email');
        }

        /** @var EntityUser $user */
        $user = Common::create_member_google([
            'id' => $response['user_id'],
            'email' => $response['email'],
            'given_name' => '',
            'family_name' => '',
        ]);
        $user->login($this->session);
        if ($user instanceof EntityUser) {
            echo json_encode( [ 'success' => true, 'user' => $user ] );
        } else {
            echo json_encode( [ 'success' => false, 'msg' => $user ] );
        }
    } catch(Exception $e) {
        echo json_encode(['success' => false, 'msg' => $e->getMessage()]);
    }