config.php

<?php
/**
 * Created by PhpStorm.
 * User: Dmitriy
 * Date: 15.10.2017
 * Time: 9:46
 */
// start session
session_start();
require_once 'vendor/autoload.php';

use Facebook\FacebookRedirectLoginHelper;
use Facebook\FacebookRequestException;
use Facebook\FacebookSession;

// init Social Media Analysis with app id and secret
FacebookSession::setDefaultApplication('1501451756809750','c6ea8a75ba70d8a2ab2ac72d0d5511fd');

// login helper with redirect_uri
$helper = new FacebookRedirectLoginHelper('http://localhost/sma/');

// see if a existing session exists
if (isset($_SESSION) && isset($_SESSION['fb_token'])) {
    // create new session from saved access_token
    $session = new FacebookSession($_SESSION['fb_token']);
    // validate the access_token to make sure it's still valid
    try {
        if (!$session->validate()) {
            $session = null;
        }
    } catch (Exception $e) {
        // catch any exceptions
        $session = null;
    }
}

if (!isset($session) || $session === null) {
    // no session exists
    try {
        $session = $helper->getSessionFromRedirect();
    } catch(FacebookRequestException $ex) {
        // when Facebook returns an error
        print_r($ex);
    } catch(Exception $ex) {
        // when validation fails or other local issues
        print_r($ex);
    }
}