gistfile1.php

<?php
require_once '../src/Google_Client.php';

function pr($content) {
	echo '<pre>';
	print_r($content);
	echo '</pre>';
}

const CLIENT_ID = 'XXXX';
const SERVICE_ACCOUNT_NAME = 'XXXX';
const KEY_FILE = 'privatekey.p12';

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

session_start();
if (isset($_SESSION['token'])) {
    echo $_SESSION['token'];
 $client->setAccessToken($_SESSION['token']);
}

$key = file_get_contents(KEY_FILE);
$client->setAssertionCredentials(new Google_AssertionCredentials(
    SERVICE_ACCOUNT_NAME,
    array(
        'https://www.googleapis.com/auth/admin.directory.user',
    	'https://www.googleapis.com/auth/admin.directory.group'
    ),
    $key)
);

$client->setClientId(CLIENT_ID);

$req = new Google_HttpRequest("https://www.googleapis.com/admin/directory/v1/groups?domain=googleappsforeducationdomain.com");
$resp = $client::getIo()->authenticatedRequest($req);
print "<h1>Single User</h1>: <pre>" . $resp->getResponseBody() . "</pre>";


if ($client->getAccessToken()) {
    pr($client->getAccessToken());
  $_SESSION['token'] = $client->getAccessToken();
}