facebook app code is failing getUser returns NULL

Question

I am trying to learn facebook app development and here s the code I am trying.

<?php
require_once 'config.php';

/* Get a valid session */
$session = $facebook->getUser();
$me = null;
if($session) {
/* Check if session is valid */
$me = $facebook->api('/me');
}

var_dump($me);
?>

I have set my app id and secret in config.php but it is failing to execute getUser(), all it returns is null.

Check it here.

http://facebookdevelop.byethost8.com/index.php

Do I need special setup to be done except copying facebook php sdk in hosting site? Is there a place where up-to date information is available which clearly defines step by step instructions?

Answer 1

You cannot just get the User ID without a user login/authorization.

See here: https://developers.facebook.com/docs/reference/php/

The Facebook docs are not as bad as so many people think. Another basic tutorial:

https://github.com/facebook/facebook-php-sdk

see "getLoginUrl". Grab the newest php sdk and use the code from "Usage" on the git page. "getUser" does not return a session, it returns a user id (or nothing/zero if the user is not logged in).

Answer 2

This code works

<?php

/**
 * This sample app is provided to kickstart your experience using Facebook's
 * resources for developers.  This sample app provides examples of several
 * key concepts, including authentication, the Graph API, and FQL (Facebook
 * Query Language). Please visit the docs at 'developers.facebook.com/docs'
 * to learn more about the resources available to you
 */

// Provides access to app specific values such as your app id and app secret.
// Defined in 'AppInfo.php'
require_once('AppInfo.php');

// Enforce https on production
if (substr(AppInfo::getUrl(), 0, 8) != 'https://' && $_SERVER['REMOTE_ADDR'] != '127.0.0.1') {
  header('Location: https://'. $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
  exit();
}

// This provides access to helper functions defined in 'utils.php'
require_once('utils.php');


/*****************************************************************************
 *
 * The content below provides examples of how to fetch Facebook data using the
 * Graph API and FQL.  It uses the helper functions defined in 'utils.php' to
 * do so.  You should change this section so that it prepares all of the
 * information that you want to display to the user.
 *
 ****************************************************************************/

require_once('sdk/src/facebook.php');

$facebook = new Facebook(array(
  'appId'  => AppInfo::appID(),
  'secret' => AppInfo::appSecret(),
  'sharedSession' => true,
  'trustForwarded' => true,
));

$user_id = $facebook->getUser();
if ($user_id) {
  try {
    // Fetch the viewer's basic information
    $basic = $facebook->api('/me');
  } catch (FacebookApiException $e) {
    // If the call fails we check if we still have a user. The user will be
    // cleared if the error is because of an invalid accesstoken
    if (!$facebook->getUser()) {
      header('Location: '. AppInfo::getUrl($_SERVER['REQUEST_URI']));
      exit();
    }
  }
  // This fetches some things that you like . 'limit=*" only returns * values.
  // To see the format of the data you are retrieving, use the "Graph API
  // Explorer" which is at https://developers.facebook.com/tools/explorer/
  $likes = idx($facebook->api('/me/likes?limit=4'), 'data', array());

  // This fetches 4 of your friends.
  $friends = idx($facebook->api('/me/friends?limit=4'), 'data', array());

  // And this returns 16 of your photos.
  $photos = idx($facebook->api('/me/photos?limit=16'), 'data', array());

  // Here is an example of a FQL call that fetches all of your friends that are
  // using this app
  $app_using_friends = $facebook->api(array(
  'method' => 'fql.query',
        'query' => 'SELECT uid, name FROM user WHERE uid IN(SELECT uid2 FROM friend WHERE uid1 = me()) AND is_app_user = 1'
  ));
}

var_dump ($user_id);
?>

Only need to figure out the difference.