Facebook SDK 4

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
session_start();
require_once( 'lib/facebook/FacebookSession.php' );
require_once( 'lib/facebook/FacebookRedirectLoginHelper.php' );
require_once( 'lib/facebook/FacebookRequest.php' );
require_once( 'lib/facebook/FacebookResponse.php' );
require_once( 'lib/facebook/FacebookSDKException.php' );
require_once( 'lib/facebook/FacebookRequestException.php' );
require_once( 'lib/facebook/FacebookAuthorizationException.php' );
require_once( 'lib/facebook/GraphObject.php' );
require_once( 'lib/facebook/Entities/AccessToken.php' );
require_once( 'lib/facebook/Entities/SignedRequest.php' );
require_once( 'lib/facebook/HttpClients/FacebookHttpable.php' );
require_once( 'lib/facebook/HttpClients/FacebookCurl.php' );
require_once( 'lib/facebook/HttpClients/FacebookCurlHttpClient.php' );

use Facebook\FacebookSession;
use Facebook\FacebookRedirectLoginHelper;
use Facebook\FacebookRequest;
use Facebook\FacebookResponse;
use Facebook\FacebookSDKException;
use Facebook\FacebookRequestException;
use Facebook\FacebookAuthorizationException;
use Facebook\GraphObject;
use Facebook\Entities\AccessToken;
use Facebook\Entities\SignedRequest;
use Facebook\HttpClients\FacebookHttpable;
use Facebook\HttpClients\FacebookCurl;
use Facebook\HttpClients\FacebookCurlHttpClient;
// init app with app id (APPID) and secret (SECRET)
FacebookSession::setDefaultApplication('xxxxxxx','xxxxx');
// login helper with redirect_uri
$helper = new FacebookRedirectLoginHelper( 'http://localhost/fb' );
try {
        $session = $helper->getSessionFromRedirect();
} catch( FacebookRequestException $ex ) {
        // When Facebook returns an error
} catch( Exception $ex ) {
        // When validation fails or other local issues
}
if ( isset( $session ) ) {
         // Dados do Utilizador
  $request = new FacebookRequest(
                   $session,
                   'GET',
                   '/me'
  );
 
$response = $request->execute();
         
$graphObject = $response->getGraphObject();
 
   echo '<a href="' . $helper->getLogoutUrl($session, 'http://localhost/fb/index.php') . '"><button type="button" class="btn btn-lg btn-success"><i class="fa fa-facebook-official fa-5x"></i> </button></a>';
} else {
   echo '<a href="' . $helper->getLoginUrl() . '"><button type="button" class="btn btn-lg btn-danger"><i class="fa fa-facebook-official fa-5x"></i></button></a>';
}
?>