php post to facebook even if i'm logged out - php

Question

I made this PHP script that fetches messages to be posted at regular intervals to a Facebook Page that I administer.
My script is working fine, but depends on me as a user being logged into Facebook. I would like this script to run as a cron job so i fear the script will fail to work if i'm logged out.
How can i make it work even if i'm not logged into Facebook?
Note that I created a Facebook application as requested to be able to use the Facebook api. Is there a way to post as the Facebook application perhaps?
Here is my code, in case it helps.
require_once('config.inc.php');
require '_classes/facebook-php-sdk/src/facebook.php';
$homeurl = 'http://domain.com/to-facebook/index.php';
$post_url = '/'.PAGEID.'/feed';
// The message
$msg_body = array(
'message' => 'hello world',
);
// Post to Facebook
$facebook = new Facebook(array(
'appId' => FB_APP_ID,
'secret' => FB_APP_SECRET,
));
// Get User ID
$fbuser = $facebook->getUser();
if ($fbuser) {
try {
$postResult = $facebook->api($post_url, 'post', $msg_body );
} catch (FacebookApiException $e) {
echo $e->getMessage();
}
}else{
// I would like never to come to this point...
$loginUrl = $facebook->getLoginUrl(array('redirect_uri'=>$homeurl,'scope'=>'publish_stream,manage_pages,publish_actions,status_update,offline_access'));
header('Location: ' . $loginUrl);
}
if($postResult)
{
echo '<h1>Your message is posted on your facebook wall.</h1>';
}
* update *
I tried the cronjob and unfortunately, after a while I had the "Error validating access token: Session has expired at unix time" message. I'm puzzled. What am i doing wrong?

Answer 1

For sites connected to your app:
When you have the app get permission to manage_pages, you run an api with your user token which gives you the access tokens of all your pages. These tokens can last forever.
For users authorizing the app:
You can make the access_token last longer. The user would need to log in to refresh the extended token however. Read up more about "Facebook Extend Token".
There used to be a permissin that gave the app the ability to reuse the token forever, but it's no longer available. The best you can do nowadays is to simply run the api to extend the token each time the user log in to your app.

Answer 2

You can easy use CURL for this. Google something like that, "CURL login, CURL facebook login"

Answer 3

**update **
I tried the cronjob and unfortunately, after a while I had the "Error validating access token: Session has expired at unix time" message. I'm puzzled. What am i doing wrong?
I seem to have found a solution based on this answer Facebook Access Token for Pages .
It explains how to get an access_token to a specific page for your FB application.
I obtained it, then adapted my code. I tested it using a browser in which i'm not logged into facebook with, and it works.
Here is the updated script in case it helps.
$msg_body = array(
'message' => $message->message.' v/ #'.$message->author,
'access_token' => FB_ACCESS_TOKEN
);
try {
$postResult = $facebook->api($post_url, 'post', $msg_body );
} catch (FacebookApiException $e) {
echo $e->getMessage();
}
if($postResult)
{
echo '<h1>Your message is posted on your facebook wall.</h1>';
print_r($msg_body);
}
I'll run the cronjob for a few days and will get back to you if it proves not to work reliably.