website #facebook app login

<?php
require 'admin/config.facebook.php';

use Facebook\Facebook;

$fb = new Facebook([
  'app_id' => $cnf["fb_appid"],
  'app_secret' => $cnf["fb_appsecret"],
  'default_graph_version' => 'v2.4',
]);

if ($_GET['f']) {
  $url_add = "?f=1";
}

if ($_GET['post_share'] && $_SESSION['TOKEN']) {
  print_r($_SESSION['TOKEN']);
  exit;
}

// login helper with redirect_uri
$helper = $fb->getRedirectLoginHelper();
$redirect_uri = $cnf["fb_appdomain"] . 'facebook.php' . $url_add;
$permissions = array(
  'scope' => 'public_profile,email,user_friends' //user_friends
);

try {
  $accessToken = $helper->getAccessToken();
} catch (FacebookRequestException $ex) {
  echo $ex;
} catch (Exception $ex) {
  echo $ex;
}
// see if we have a session
$_SESSION['FBCODE'] = $_REQUEST['code'];


if (isset($accessToken)) {
  $fb->setDefaultAccessToken((string)$accessToken);
  $response = $fb->get('/me?locale=en_US&fields=id,name,email');
  $userNode = $response->getGraphUser();

  $fbid = $userNode->getProperty('id');              // To Get Facebook ID
  $fbfullname = $userNode->getProperty('name'); // To Get Facebook full name
  $femail = $userNode->getProperty('email');    // To Get Facebook email ID

  if (!$url_add) {
    $_SESSION['FBID'] = $fbid;
    $_SESSION['FULLNAME'] = $fbfullname;
    $_SESSION['EMAIL'] = $femail;
    $_SESSION['TOKEN'] = (string)$accessToken;
    $_SESSION['login_3rd'] = "fb";
    $_SESSION['LOGOUT'] = $helper->getLogoutUrl($accessToken, $cnf["fb_appdomain"] . "/logout-fb");
      header("Location: /game-card");
  } else {
    $_SESSION['F_FBID'] = $fbid;
    $_SESSION['F_FULLNAME'] = $fbfullname;
    $_SESSION['F_EMAIL'] = $femail;
    $_SESSION['F_TOKEN'] = (string)$accessToken;
    $_SESSION['F_LOGOUT'] = $helper->getLogoutUrl($accessToken, $cnf["fb_appdomain"] . "/moi-ban");
    header("Location: /home");
  }

} else {
  $loginUrl = $helper->getLoginUrl($redirect_uri, $permissions);
  header("Location: " . $loginUrl);
}

exit;