google api calendar php - php

Question

I am aware many similar questions have been asked, but I am struggling to understand. I have successfully used the php google libraries for v3 to interface with calendar functions. The code I have is:
<?php
require_once "google-api-php-client/autoload.php";
session_start();
$client = new Google_Client();
$client->setApplicationName("My app");
$client->setClientId("CI.apps.googleusercontent.com");
$client->SetClientSecret("SECRET");
$client->setRedirectUri("redirect");
$client->setDeveloperKey("key");
$client->setScopes(array("https://www.googleapis.com/auth/calendar"));
if (isset($_REQUEST['logout'])) {
unset($_SESSION['access_token']);
}
if (isset($_GET['code'])) {
$client->authenticate($_GET['code']);
$_SESSION['access_token'] = $client->getAccessToken();
$redirect = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
header('Location: ' . filter_var($redirect, FILTER_SANITIZE_URL));
}
if (isset($_SESSION['token'])) {
$client->setAccessToken($_SESSION['token']);//update token
}
$service=new Google_Service_Calendar($client);
...
?>
This works ok, but the calendar I want to modify is always the same- the app is registered at the same account as the calendar. Is there a way round the oauth2 authentication so that I can just adjust the entries in the calendar which I own without having to perform an extra authentication step with redirect? I used to use Zend to do this and it worked fine until recently, but updating to v3 of the API and using oauth2 like this seems a bit overkill. I may have misunderstood of course - any help of advice would me most helpful.

Answer 1

Ok - in case anyone else searches for the answer to this I thought I'd post my solution. I was a bit stupid. If you want to authenticate an application to modify a calendar in this way you need to create a service account in the google console - not a web application. Then you need to use the service account name (e-mail address given to the Client ID for the service account) to allow the script to modify the calendar. Do this manually by going to the setting of the calendar you want to modify. This code will then work fine.
<?php
session_start();
require_once "google-api-php-client/autoload.php";
$client_id = ''; //Client ID
$service_account_name = ''; //Email Address
$key_file_location = ''; //key.p12
$client = new Google_Client();
$client->setApplicationName("my app");
$service = new Google_Service_Calendar($client);
if (isset($_SESSION['service_token'])) {
$client->setAccessToken($_SESSION['service_token']);
}
$key = file_get_contents($key_file_location);
$cred = new Google_Auth_AssertionCredentials(
$service_account_name,
array('https://www.googleapis.com/auth/calendar'),
$key
);
$client->setAssertionCredentials($cred);
if ($client->getAuth()->isAccessTokenExpired()) {
$client->getAuth()->refreshTokenWithAssertion($cred);
}
$_SESSION['service_token'] = $client->getAccessToken();?>