google-api-php-client connect with key.p12 - php

Question

I'm able to add event to my google calendar with an API keys and OAuth 2.0 client IDs but I want to do this without the authorization screen of google.
I followed the information found on this post:
stackoverflow.com/questions/8995451/how-do-i-connect-to-the-google-calendar-api-without-the-oauth-authentication
For this, I created a 'Service account keys'. I went to my project credentials and select 'Create Credentials > Service Account Key'
Then:
service account > my_project_name
Key type > p12
I saved the key file key.p12
Here is my code:
<?php
// display error, debbug
ini_set('display_errors',1);
session_start();
require_once './google-api-php-client/src/Google_Client.php';
require_once './google-api-php-client/src/contrib/Google_CalendarService.php';
// following values are taken from : console.developers.google.com/apis/credentials?project=projectname credentials
// OAuth 2.0 client IDs : Client ID
const CLIENT_ID = 'xxxx';
// Service account keys : Service account
const SERVICE_ACCOUNT_NAME = 'my_project_name';
// key
const KEY_FILE = './key.p12';
$client = new Google_Client();
$client->setApplicationName("Google Calendar API Quickstart");
if (isset($_SESSION['token'])) {
$client->setAccessToken($_SESSION['token']);
}
// Load the key in PKCS 12 format
$key = file_get_contents(KEY_FILE);
$client->setAssertionCredentials(new Google_AssertionCredentials(
SERVICE_ACCOUNT_NAME,
array('https://www.googleapis.com/auth/calendar'),
$key)
);
$client->setClientId(CLIENT_ID);
$cal = new Google_CalendarService($client);
//Save token in session
if ($client->getAccessToken()) {
$_SESSION['token'] = $client->getAccessToken();
}
// my code here
$event = new Google_Event(...
$calendarId = 'mycalendarID#group.calendar.google.com';
$event = $cal->events->insert($calendarId, $event);
?>
And here is the error message:
Fatal error: Uncaught Google_AuthException: Error refreshing the OAuth2 token, message: '{
'error' : 'invalid_client',
'error_description' : 'The OAuth client was not found.'
}' in /home/www/google-api-php-client/src/auth/Google_OAuth2.php:288
Stack trace:
#0 /home/www/google-api-php-client/src/auth/Google_OAuth2.php(264): Google_OAuth2->refreshTokenRequest(Array)
#1 /home/www/google-api-php-client/src/auth/Google_OAuth2.php(218): Google_OAuth2->refreshTokenWithAssertion()
#2 /home/www/google-api-php-client/src/service/Google_ServiceResource.php(167): Google_OAuth2->sign(Object(Google_HttpRequest))
#3 /home/www/google-api-php-client/src/contrib/Google_CalendarService.php(469): Google_ServiceResource->__call('insert', Array)
#4 /home/www/goog in /home/www/google-api-php-client/src/auth/Google_OAuth2.php on line 288
It seems that the $client->getAccessToken() isn't set but I don't know why.
Thanks in advance for your help.

Answer 1

Create service account key and download the *.json file that contains private keys. Put the *.json file you just downloaded in a directory of your choosing ( credentials.json file in the example ). Then go to Google Calendar->Share and add service account id on the list.
putenv( 'GOOGLE_APPLICATION_CREDENTIALS=credentials.json' );
$client = new Google_Client();
$client->useApplicationDefaultCredentials();
$client->addScope( 'https://www.googleapis.com/auth/calendar' );
$client->setHttpClient( new GuzzleHttp\Client( [ 'verify' => false ] ) ); // disable ssl if necessary
$service = new Google_Service_Calendar( $client );
// list events
$service->events->listEvents( $calendar_id, array( 'timeMin' => ( new DateTime )->format( DateTime::RFC3339 ) ) );
// add event
$event = new Google_Service_Calendar_Event( $data );
$event = $service->events->insert( $calendar_id, $event );
You can find the Google APIs PHP Client Library package with autoloader in the releases page on GitHub, so the only require_once call necessary is for autoload file:
require_once '/path/to/google-api-php-client/vendor/autoload.php';
And, Google docs may help you further, this is just one way that works for me so it may be useful to you as well.