Facebook Graph Error This authorization code has expired - php

Question

Hi Sir Am Using Fb Php Sdk 4 & Graph 2.8 I Know Its Little Outdated But I Want Continue On It. Only Authorized Problem Fixed Can Make My Project Done
I Used Configured & Login Data Page Below But Its Return Me
Graph returned an error: This authorization code has been used.
below my code
config.php
<?php
session_start();
$_IM=array(
"sitename" => "AppsFunny",
"siteurl" => "http://appsfunny.com",
"sitelogo" => "AppsFunny.Com",
"fb_page" => "/appsfunny",
"aurl" => "appsfunny.com"
);
include "ifunc.php";
include "db.php";
include "Unicode2Bijoy.class.php";
$app_id='423436984657946';
require_once __DIR__ . '/vendor/autoload.php';
use Facebook\FacebookRequest;
$fb = new Facebook\Facebook([
'app_id' => $app_id,
'app_secret' => 'c82ff16cec2f6a055302c5c632c0129b',
'default_graph_version' => 'v2.8',
]);
if (isset($_SESSION['access_token'])) {
$token = $session->getToken();
try {
// Returns a `Facebook\FacebookResponse` object
$response = $fb->get('/me', $token);
} catch(Facebook\Exceptions\FacebookResponseException $e) {
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
$user = $response->getGraphUser();
$_SESSION['FBID'] = $user['id'];
$_SESSION['FULLNAME'] = $user['name'];
$_SESSION['propic']="https://graph.facebook.com/".$_SESSION['FBID']."/picture?height=200&width=200";
}
?>
and login.php
<?php
require_once __DIR__ . '/config.php';
$p=$_GET["p"];
$helper = $fb->getRedirectLoginHelper();
$_SESSION['FBRLH_state']=$_GET['state'];
try {
$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: ' . $e->getMessage();
exit;
}
if (isset($accessToken)) {
$access_token = $session->getToken();
$_SESSION['access_token'] = (string) $accessToken;
header("location:".$p);
}

Answer 1

Cause
This problem is there because you are trying to request access_token on every page load or reload. When you request a token, a unique code is get passed along with the URL. When you request again and again with the same token, this error occurs.
Solution
So after getting access_token, keep it in db. And request for new token only and only if either you don't have access_token or its not valid anymore.