How to make user object available across pages in CodeIgniter?

I'm fairly new to CodeIgniter and I'm using Ion Auth for user authorization. With t开发者_开发问答he Ion Auth library, you get a user object like:

  $user = $this->ion_auth->get_user();
  echo $user->email;

If a user is logged in, I want the $user object to be available on any of the pages (in any of the controllers). How can I do this? (I'm using CodeIgniter 2)

This blog post of mine goes into a lot of detail in specifically using Ion_Auth to allow your entire application (including views) to access your current user's information.

The short version... (specifically for the topic at hand)

Adding this to your MY_Controller.php file

class User_Controller extends CI_Controller {

    protected $the_user;

    public function __construct() {

        parent::__construct();

        if($this->ion_auth->logged_in()) {
            $data->the_user = $this->ion_auth->get_user();
            $this->the_user = $data->the_user;
            $this->load->vars($data);
        }
        else {
            redirect('/');
        }
    }
}

Then in your application just create your controller like this

class App_Controller extends User_Controller {

    public function __construct() {
        parent::__construct();
    }

    function index() {
        //do stuff
    }
}

Then not only in your controller will you have access to $this->the_user but you will also have $the_user loaded into every view with $this->load->vars()

Normally you'd cache something like this in the session, however I've moved away from that in most of my CI apps.

An example: you log the user in (caching the user data) and then they go to update their email on their profile page. You now have to reload you cache. Many other things could drive this reload. Usually the most I cache any more is the ID, then I do what you're doing and get the user's data on any page I need it.

One thing I found that helps is to have base controllers. For example I have a RegisteredUserController. Any controller whose actions all require the user to be logged in extend this. That way I can keep the logged in check and things like get the user data in one spot (in the constructor). For example:

class RegisteredUserController extends CI_Controller {
    var $user;

    function  __construct()  {
        parent::__construct();
            $this->user = $this->ion_auth->get_user();
        }
}

Then any controller that extends RegisteredUserController instead of just controller can get to the user with $this->user. Following this pattern would get it on every page (that extends the controller) without resorting to caching.