Facebook PHP SDK - how to get a long lived page access token - php

Question

Having this code, which works:
$appsecretProof = hash_hmac('sha256', $shortLivedToken, $secret);
//init curl
$ch = curl_init();
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
curl_setopt($ch, CURLOPT_TIMEOUT, 60);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_USERAGENT, 'facebook-php-3.2');
//get extended user access token
$url = 'https://graph.facebook.com/oauth/access_token?grant_type=fb_exchange_token' .
'&client_id=' . $appId .
'&client_secret=' . $secret .
'&fb_exchange_token=' . $shortLivedToken .
'&appsecret_proof=' . $appsecretProof;
curl_setopt($ch, CURLOPT_URL, $url);
$curlResult = curl_exec($ch);
$response_params = [];
parse_str($curlResult, $response_params);
$extendedUserToken = $response_params['access_token'];
$appsecretProof = hash_hmac('sha256', $extendedUserToken, $secret);
//get extended page access token
$url = 'https://graph.facebook.com/' . $pageId .
'?fields=access_token' .
'&access_token=' . $extendedUserToken .
'&appsecret_proof=' . $appsecretProof;
curl_setopt($ch, CURLOPT_URL, $url);
$curlResult = curl_exec($ch);
curl_close($ch);
$pageToken = json_decode($curlResult)->access_token;
How to achieve the same using the regular Facebook SDK? Googling didn't really help. Either I find nothing usable or the solutions do not work, throwing errors like "An access token is required to request this resource" or similar stuff. I already tried a lot but nothing really works.
My last approach was:
FacebookSession::setDefaultApplication($appId, $secret);
$shortLivedSession = new FacebookSession($shortLivedToken);
$shortLivedSession->getLongLivedSession();
$request = new FacebookRequest($shortLivedSession, 'GET', '/' . $pageId . '?fields=access_token');
$response = $request->execute();
$result = $response->getGraphObject()->asArray();
$pageToken = $result['access_token'];
$facebookSession = new FacebookSession($pageToken);
This code always returns a short-lived token.

Answer 1

Figured it out and #luschn, there seems to be the same error in the code on your blog.
What helped was to replace these two lines:
$shortLivedSession->getLongLivedSession();
$request = new FacebookRequest($shortLivedSession, 'GET', '/' . $pageId . '?fields=access_token');
with these:
$longLivedSession = $shortLivedSession->getLongLivedSession();
$request = new FacebookRequest($longLivedSession, 'GET', '/' . $pageId . '?fields=access_token');