Google+ Auth for Google apps

gistfile1.php

<?php
require_once 'google-api-php-client/src/Google_Client.php';
require_once 'google-api-php-client/src/contrib/Google_PlusService.php';
require_once 'google-api-php-client/src/contrib/Google_Oauth2Service.php';

// Set your cached access token. Remember to replace $_SESSION with a
// real database or memcached.
session_start();

$client = new Google_Client();
$client->setApplicationName('Google+ PHP Starter Application');
// Visit https://code.google.com/apis/console?api=plus to generate your
// client id, client secret, and to register your redirect uri.
$client->setClientId('');
$client->setClientSecret('');
$client->setRedirectUri('');
$client->setDeveloperKey('');
$client->setScopes(array('https://www.googleapis.com/auth/userinfo.email',
        'https://www.googleapis.com/auth/plus.me')); 
$plus = new Google_PlusService($client);

if (isset($_GET['code'])) {
 $oauth2 = new Google_Oauth2Service($client);

  // Authenticate the user, $_GET['code'] is used internally:
  $client->authenticate();

  // Will get id (number), email (string) and verified_email (boolean):
  $user = $oauth2->userinfo->get();  
  if ($user["hd"] == "santexgroup.com") {
    //set user if the domain is correct
    $_SESSION['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']);
}

if (!$client->getAccessToken()) {
  $authUrl = $client->createAuthUrl();
  print '<a href="'.$authUrl.'""><img src="img/login.png"></a>';
} else { //we are logged in! 
?>