How to fix "fb_exchange_token parameter not specified"? - facebook-graph-api

Question

I cannot find any documentation on this.
Here is my code:
I'm using Laravel 5.5 and Facbook graph. Im posting to a page but I got this error fb_exchange_token parameter not specified but I have successfully logged in.
Due to shoddy documentation I cannot find anything on fb_exchange_token on the Facebook's website nor elsewhere.
Can anyone help?
{
$facebook = Facebooks::findOrFail($id);
$fb = new Facebook([
'app_id' => 'my_id', // Replace {app-id} with your app id
'app_secret' => 'my_secret',
'default_graph_version' => 'v3.3',
]);
$helper = $fb->getRedirectLoginHelper();
$permissions = ['manage_pages', 'publish_pages']; // optional
try {
if (isset($_SESSION['facebook_access_token'])) {
$accessToken = $_SESSION['facebook_access_token'];
} else {
$accessToken = $helper->getAccessToken();
}
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
if (isset($_SESSION['facebook_access_token'])) {
$fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
} else {
// getting short-lived access token
$_SESSION['facebook_access_token'] = (string) $accessToken;
// OAuth 2.0 client handler
$oAuth2Client = $fb->getOAuth2Client();
// Exchanges a short-lived access token for a long-lived one
$longLivedAccessToken = $oAuth2Client->getLongLivedAccessToken($_SESSION['facebook_access_token']);
$_SESSION['facebook_access_token'] = (string) $longLivedAccessToken;
// setting default access token to be used in script
$fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
}
// redirect the user back to the same page if it has "code" GET variable
if (isset($_GET['code'])) {
header('Location: ./');
}
// getting basic info about user
try {
$profile_request = $fb->get('/me');
$profile = $profile_request->getGraphNode()->asArray();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
session_destroy();
// redirecting user back to app login page
header("Location: ./");
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
// post on behalf of page
$pages = $fb->get('/me/accounts');
$pages = $pages->getGraphEdge()->asArray();
foreach($pages as $key){
if($key['name'] == 'CloudGuest Test'){
if(isset($_POST['facebook_status'])){
$text1 = $_POST['facebook_status'];
$post = $fb->post('/' . $key['id'] . '/feed', array('message' =>$text1),$key['access_token']);
$post = $post->getGraphNode()->asArray();
print_r($post);
}
}
}
}