If I’m not wrong, they’ve launched Service Account for this now: https://developers.google.com/accounts/docs/OAuth2ServiceAccount
Edit:
Here’s the modification from their Prediction API
session_start();
require_once "google-api-php-client/src/Google_Client.php";
require_once "google-api-php-client/src/contrib/Google_CalendarService.php";
const CLIENT_ID = '...';
const SERVICE_ACCOUNT_NAME = '...';
// Make sure you keep your key.p12 file in a secure location, and isn't
// readable by others.
const KEY_FILE = '...';
$client = new Google_Client();
$client->setApplicationName("...");
if (isset($_SESSION['token'])) {
$client->setAccessToken($_SESSION['token']);
}
// Load the key in PKCS 12 format (you need to download this from the
// Google API Console when the service account was created.
$key = file_get_contents(KEY_FILE);
$client->setAssertionCredentials(new Google_AssertionCredentials(
SERVICE_ACCOUNT_NAME,
array('https://www.googleapis.com/auth/calendar', "https://www.googleapis.com/auth/calendar.readonly"),
$key)
);
$client->setClientId(CLIENT_ID);
$service = new Google_CalendarService($client);
//Save token in session
if ($client->getAccessToken()) {
$_SESSION['token'] = $client->getAccessToken();
}
//And now you can use the code in their PHP examples, like: $service->events->listEvents(...)