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phpgoogle-calendar-apigoogle-appsgoogle-oauth

How to create Google calendar entry w/o user?

Recently I've decided to give users at my site the following functionality: online time slot booking in calendars of my employees. All employees have Google accounts linked to our domain in Google Apps (free edition). Users make booking in some front-end (e.g. not directly in employees Google calendars), then request is processed at our PHP server and if it is correct, server should be able to create new calendar entry in selected employee Google calendar. Note - neither user, nor employee should not be asked for authentication during booking.

I've scanned Google calendar v3 API and forums and still didn't get neither clear answer not concise examples - is such scenario possible with Google calendar? Can someone help me to answer the Q (and if possible - share a link with proper example)?

Solution

  • Are you familiar with adding an event with authentication? Like i answered here.
    And like in the code below. If you are... you can go to the next level ;)

    (You can download the Google Api Php-client on this page. On this page there is a tutorial. It's for Google+ but the principle is the same)

    The first time you would always need authentication. There is no way around that. In the example below you get a token back after authentication, which includes an access_token and a refresh_token. The access_token is only valid for 3600 seconds and is used for direct access. When the access_token is expired you get a 401 error and you can use the refresh_token (together with client_id, client_secret and the correct grant_type) to request a new access_token.

    You can find some more information on this page (at the bottom "Using a Refresh Token"). There are some limits in numbers to request these, mentioned on that page at the bottom.

    This is some testing code i made the last time i helped someone with this. It only shows getting the authentication and storing the token in a cookie. It does not request a new access_token after it expires.

    But as i already said you need to store the token (in a database?) and when you get a 401 you need to request a new access_token with the client_id, client_secret, correct grant_type and refresh_token. There is no (re-)authentication necessary for that.

    <?php
error_reporting(E_ALL);
require_once 'google-api-php-client/src/Google_Client.php';
require_once 'google-api-php-client/src/contrib/Google_CalendarService.php';
session_start();

if ((isset($_SESSION)) && (!empty($_SESSION))) {
   echo "There are cookies<br>";
   echo "<pre>";
   print_r($_SESSION);
   echo "</pre>";
}

$client = new Google_Client();
$client->setApplicationName("Google Calendar PHP Starter Application");
$client->setClientId('###');
$client->setClientSecret('###');
$client->setRedirectUri('http://###/add_calendar.php'); // <- registered web-page
//$client->setDeveloperKey('###'); // <- not always needed
$cal = new Google_CalendarService($client);

if (isset($_GET['logout'])) {
  echo "<br><br><font size=+2>Logging out</font>";
  unset($_SESSION['token']);
}

if (isset($_GET['code'])) {
  echo "<br>I got a code from Google = ".$_GET['code']; // You won't see this if redirected later
  $client->authenticate(); // $_GET['code']
  $_SESSION['token'] = $client->getAccessToken();
  header('Location: http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF']);
  // not strictly necessary to redirect but cleaner for the url in address-bar
  echo "<br>I got the token = ".$_SESSION['token']; // <-- not needed to get here unless location uncommented
}

if (isset($_SESSION['token'])) {
  echo "<br>Getting access";
  $client->setAccessToken($_SESSION['token']);
}

if ($client->getAccessToken()){
  echo "<hr><font size=+1>I have access to your calendar</font>";
  $event = new Google_Event();
  $event->setSummary('=== I ADDED THIS ===');
  $event->setLocation('The Neighbourhood');
  $start = new Google_EventDateTime();
  $start->setDateTime('2013-11-29T10:00:00.000-05:00');
  $event->setStart($start);
  $end = new Google_EventDateTime();
  $end->setDateTime('2013-11-29T10:25:00.000-05:00');
  $event->setEnd($end);
  $createdEvent = $cal->events->insert('###', $event); // <- ### = email of calendar
  echo "<br><font size=+1>Event created</font>";

  echo "<hr><br><font size=+1>Already connected</font> (No need to login)";

} else {

  $authUrl = $client->createAuthUrl();
  print "<hr><br><font size=+2><a href='$authUrl'>Connect Me!</a></font>";

}

$url = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
echo "<br><br><font size=+2><a href=$url?logout>Logout</a></font>";

?>

    Edit:

    If you don't want the initial authentication Google has its "Service Acounts", as you pointed out.
    (I didn't know about these :)

    I dug up some links where you can find code to use after you got the key-file.

    Edit Google calendar events from Google service account: 403
    Access Google calendar events from with service account: { "error" : "access_denied" }. No google apps
    Google OAuth 2.0 Service Account - Calendar API (PHP Client)
    https://groups.google.com/forum/#!topic/google-api-php-client/B7KXVQvx1k8
    https://groups.google.com/forum/?fromgroups#!topic/google-api-php-client/IiwRBKZMZxw

    Edit #2: YES, got it working. (even with my free Google account ;)

    Here is the working code:

    <?
error_reporting(E_ALL);
require_once 'google-api-php-client/src/Google_Client.php';
require_once 'google-api-php-client/src/contrib/Google_CalendarService.php';
session_start();

echo "Busy<br>";

const CLIENT_ID = 'xxxxxxxxxx.apps.googleusercontent.com';
const SERVICE_ACCOUNT_NAME = '[email protected]';
const KEY_FILE = 'xxxxxxxxxxxxxxxxxxx-privatekey.p12';
const CALENDAR_NAME = '[email protected]';

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

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

$key = file_get_contents(KEY_FILE);
$client->setClientId(CLIENT_ID);
$client->setAssertionCredentials(new Google_AssertionCredentials(
  SERVICE_ACCOUNT_NAME,
  array('https://www.google.com/calendar/feeds/'),
  $key)
);

$client->setClientId(CLIENT_ID);
$service = new Google_CalendarService($client);

$event = new Google_Event();
$event->setSummary('=== I MADE THIS ===');
$event->setLocation('Somewhere else');
$start = new Google_EventDateTime();
$start->setDateTime('2013-11-30T10:00:00.000-02:00');
$event->setStart($start);
$end = new Google_EventDateTime();
$end->setDateTime('2013-11-30T10:25:00.000-02:00');
$event->setEnd($end);

$createdEvent = $service->events->insert(CALENDAR_NAME, $event);

echo "Done<br>";

?>

    I needed to make a "new project" on https://cloud.google.com/console#/project. I couldn't use the existing one. After activating "Calendar API" and registering a new Web-app with Certificate i only needed to share my calendar with the [email protected] and above code worked
    (without authentication).

    Edit #3: and now it also seems to be working in the default "Google+ API Project"