When using CodeIgniter + Facebook PHP SDK: getUser() always returns 0-open source projects facebookarchive/facebook-php-sdk

I am attempting to use the Facebook PHP SDK in conjunction with CodeIgniter to allow users to login to my site using Facebook Connect. No matter what I try, getUser() always returns 0, even after (apparently) successful authentication via Facebook.

CodeIgniter version: 2.1.3

Facebook PHP SDK version: 3.2.2

I have created a config file, facebook.php, in the application/config folder and I am loading the Facebook PHP SDK via CodeIgniter’s $this->load->library(…) method. The library is indeed getting loaded and I can successfully call many of the get…() methods including getAccessToken(), getAppId() and getAppSecret(), all of which return their expected values.

Here is a stripped down version of my login controller: (note that I also provide an alternate method of logging in via email, hence the CodeIgniter session code sprinkled throughout)

class Login extends CI_Controller {

    public function __construct()
    {
        //Call parent constructor
        parent::__construct();

        //Magic sauce - not sure if this is required but a lot of other people
        //are recommending it to be included (happy to remove it if necessary)
        parse_str($_SERVER['QUERY_STRING'], $_REQUEST);

        //Load facebook library
        $facebook_config = $this->load->config('facebook');
        $this->load->library('facebook', $facebook_config);
    }

   public function index()
    {
        //Check if user is logged in
        $user_id = $this->session->userdata('user_id');
        $is_logged_in = $this->session->userdata('is_logged_in');

        if(($is_logged_in) && ($user_id != 0)) {
            //Logged in - redirect to game
            redirect('game');
        } else {
            //Not logged in
            //Get facebook login url
            $facebook_data = array(
                'redirect_uri' => 'hxxp://xxxxxxxx.com/facebook_login/',
                'scope' => 'email'
            );
            $data['facebook_login_url'] = $this->facebook->getLoginUrl($facebook_data);
            //Redirect to login form
            $this->load->view('login/login_form', $data);
        }
    }

    public function facebook_login()
    {
        //Always returns 0!! Even after authenticating via facebook!
        $facebook_user_id = $this->facebook->getUser();

        if ($facebook_user_id) {
            try {
                $user_profile = $this->facebook->api('/me');
                print_r($user_profile);
            } catch (FacebookApiException $e) {
                echo $e->getMessage();
            }
        } else {
            echo "Could not log in with Facebook";
        }
    }
}

The stripped down view (login_form.php) is as follows:

    
        Facebook Connect Test