Example callback url from facebook sdk using php

login-callback.php

<?php
# login-callback.php
session_start();
require_once './Facebook/autoload.php';
$fb = new Facebook\Facebook([
  'app_id' => '1902403916702759',
  'app_secret' => '2644a874fd4d7801db5d2e68f9e26d3b',
  'default_graph_version' => 'v2.5',
]);
$helper = $fb->getRedirectLoginHelper();
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)) {
  // Logged in!
  $_SESSION['facebook_access_token'] = (string) $accessToken;
  // Now you can redirect to another page and use the
  // access token from $_SESSION['facebook_access_token']
    $fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
    try {
      $response = $fb->get('/me?locale=en_US&fields=name,email,first_name,last_name');  //https://developers.facebook.com/docs/facebook-login/permissions
      $userNode = $response->getGraphUser();
    } 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;
    }
    echo 'Logged in as ' . $userNode->getName();
}
?>