On a Codeigniter project I’m working on, I wanted to have Twitter and Facebook logins available. Luckily, right around the time I was starting the project, Elliot Haughin released libraries for both Twitter and Facebook. The Twitter library worked almost instantly and is quite brilliant. However, the Facebook library was causing me some problem.

Looking through the Facebook Developer pages, it seemed like a fairly straight-forward process to get a User’s Facebook auth tokens… and with CI2 having querystring support now, I thought I could do everything in a simple Facebook controller.  Here’s what I got:

<?php

if (!defined('BASEPATH'))
    exit('No direct script access allowed');

/**
 * Name:  Simple Facebook Codeigniter Login
 *
 * Author: Terry Matula
 *         terrymatula@gmail.com
 *         @terrymatula

 * Created:  03.31.2011
 *
 * Description:  An easy way to use Facebook to login
 *
 * Requirements: PHP5 or above
 *
 */
class Facebook extends CI_Controller {

    public $appid;
    public $apisecret;

    public function __construct()
    {
        parent::__construct();
        // replace these with Application ID and Application Secret.
        $this->appid = '12345';
        $this->apisecret = '123abc123';
    }

    /**
     * if you have a Facebook login button on your site, link it here
     */
    public function index()
    {
        // set the page you want Facebook to send the user back to
        $callback = site_url('facebook/confirm');
        // create the FB auth url to redirect the user to. 'scope' is
        // a comma sep list of the permissions you want. then direct them to it
        $url = "https://graph.facebook.com/oauth/authorize?client_id={$this->appid}&redirect_uri={$callback}&scope=email,publish_stream";
        redirect($url);
    }

    /**
     * Get tokens from FB then exchanges them for the User login tokens
     */
    public function confirm()
    {
        // get the code from the querystring
        $redirect = site_url('facebook/confirm');
        $code = $this->input->get('code');
        if ($code)
        {
            // now to get the auth token. '__getpage' is just a CURL method
            $gettoken = "https://graph.facebook.com/oauth/access_token?client_id={$this->appid}&redirect_uri={$redirect}&client_secret={$this->apisecret}&code={$code}";
            $return = $this->__getpage($gettoken);
            // if CURL didn't return a valid 200 http code, die
            if (!$return)
                die('Error getting token');
            // put the token into the $access_token variable
            parse_str($return);
            // now you can save the token to a database, and use it to access the user's graph
            // for example, this will return all their basic info.  check the FB Dev docs for more.
            $infourl = "https://graph.facebook.com/me?access_token=$access_token";
            $return = $this->__getpage($infourl);
            if (!$return)
                die('Error getting info');
            $info = json_decode($return);
            print_r($info);
        }
    }

    /**
     * CURL method to interface with FB API
     * @param string $url
     * @return json
     */
    private function __getpage($url)
    {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        $return = curl_exec($ch);
        $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        // check if it returns 200, or else return false
        if ($http_code === 200)
        {
            curl_close($ch);
            return $return;
        }
        else
        {
            // store the error. I may want to return this instead of FALSE later
            $error = curl_error($ch);
            curl_close($ch);
            return FALSE;
        }
    }

}

That’s about it. You could put it all in “index()”, but I wanted to separate it a little.

update: Looking at the bit.ly api, it’s actually very similar. i’ll eventually try to make it more generic.