How to clear all events in Google Calendar using API V3 PHP - google-calendar-api

Question

I spent a long time to work out how to do the following using Google Calendar using API V3 in PHP
insert a new event
read all existing events
delete each existing event
However I would still like to know how to clear an entire Google Calendar to make my code faster, as the read & delete method is a little slow.
I've been trying to work out how to use the supplied Google function "clear" for this, and the documentation supplied by Google simply shows that I should be able to use the following command to achieve this:
$service->calendars->clear('primary');
Also within the Google Code there is a comment relating to the "calendars" collection of methods (where the clear function exists):
Typical usage is:
<code>
$calendarService = new Google_Service_Calendar(...);
$calendars = $calendarService->calendars;
</code>
So I've put this together with the preceding authentication code. I am sure the authentication is working OK as I've used that elsewhere, but the clear code is obviously wrong as I get error message:
Notice: Undefined variable: service in C:\wamp\www\googleapi\clear\index.php on line 39
I've tried using 'primary' as well as the main owner, and I've tried making the calendar private and public but to no avail.
Anyone who has got the clear method to work, please point me in the right direction.
This is the code I'm running so far:
<?php
session_start();
require_once '../google-api-php-client-master/autoload.php';
//Google credentials
$client_id = 'xxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com';
$service_account_name = 'xxxxxxxxxxxxxxxxxxxxxx#developer.gserviceaccount.com';
$key_file_location = '../google-api-php-client-master/API Project-xxxxxxx.p12';
if (!strlen($service_account_name) || !strlen($key_file_location))
echo missingServiceAccountDetailsWarning();
$client = new Google_Client();
$client->setApplicationName("Whatever the name of your app is");
if (isset($_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()) {
try {
$client->getAuth()->refreshTokenWithAssertion($cred);
} catch (Exception $e) {
var_dump($e->getMessage());
}
}
$_SESSION['service_token'] = $client->getAccessToken();
/* ------------------------- We are now properly authenticated ------------------- */
$calendarService = new Google_Service_Calendar($client);
$calendars = $calendarService->calendars;
$service->calendars->clear('primary');
?>

Answer 1

Just use your service calendar instance.
$service = new Google_Service_Calendar($client);
$calendar = $service->calendars->clear('primary');