Using facebook off-line access to post on user's wall

Important notice! There was change in API in May 1, 2012. "offline_access" permission was deprecated. Quote: "For existing apps, there are no changes required for your app, but you should consider using the new endpoint". I have to re-write or add fallow up articles to my posts about "offline_access" permission about that suggestion/change. I also have to modify my example and live apps. But AFAIK - there is no hurry, because nothing gets broken that day. Read more about it here

Notice: This article is updated (july 2011) after initial publish because of changes in facebook API.

This is simplified and robust example how you can post on user's wall when she/he is not currently logged in or not using your application. It's achieved by by using stored access_token. Access tokens are needed to make calls on facebook graph api. Before that user has to allow offline_access permissions to your app. But let's take it step by step.

Also you may check out my previous post where I shared simple example of facebook iframe app with new php-sdk API. That would be good starting point if you are not familiar with facebook app development yet. And here is example app which uses this offline access permission.

This article uses $facebook object in examples. So before trying any of this out, create new facebook instance at the beginning of the script. It should look something like this.

//add php-sdk
require './facebook.php';

//Create facebook instance.
$facebook = new Facebook(array(
  'appId'  => 'application ID',
  'secret' => 'application secret',
  'cookie' => true,
));

Authorising url

First we need user to accept off-line access. When creating authorise url for your app, add 'offline_access' permission along others. This will grant permission to make such calls. This specific url is just a example but important part is here is req_perms parameter.

$loginUrl = $facebook->getLoginUrl(array(
	'canvas' => 1,
	'fbconnect' => 0,
	'req_perms' => 'publish_stream,offline_access',
	'next' => 'APP CANVAS URL IN FACEBOOK',
	'cancel_url' => 'URL WHERE TO REDIRECT WHEN ACCESS NOT GRANTED',
));

$loginUrl = $facebook->getLoginUrl(array(
	'canvas' => 1,
	'fbconnect' => 0,
	'scope' => 'offline_access,publish_stream'
));

Getting the token

If session is established, you can obtain it from session variables. That is all. Now you can store it in database or wherever you like and use it in your script when needed.

//get session
$session = $facebook->getSession();

//print out token stored in session
//using this you can do api calls even if
//user is not currently interacting with your app
if ($session) {
	echo $session['access_token'];
}

$user = $facebook->getUser();
if($user){
	echo $facebook->getAccessToken();
}

Using token for posting

Now the actual offline posting part. This is very simple. You only need that token gained earlier. This example shows how to post message on user's wall and get user's data. Also $res variable (array) will hold post ID if successfully posted. Code would be following.

//create message with token gained before
$post =  array(
	'access_token' => 'TOKEN HERE',
	'message' => 'This message is posted with access token - ' . date('Y-m-d H:i:s')
);

//and make the request
$res = $facebook->api('/me/feed', 'POST', $post);

//For example this can also be used to gain user data
//and this time only token is needed
$token =  array(
	'access_token' => 'TOKEN HERE'
);
$userdata = $facebook->api('/me', 'GET', $token);

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