CI layout demonstrated by Shawn McCool heybigname.com/2011/08/26/codeigniter-2-sparks-php-activerecord-part-4-views-and-layouts/

controllers_auth.php

<?php

class Auth extends MY_Controller
{
    function login()
    {
        if ($_POST)
        {
            // The user has submitted the login form
            $user = User::validate_login($_POST['username'], $_POST['password']);

            if ($user)
                redirect('dashboard');
            else
                $this->view_data['message'] = 'Invalid user/password.';
        }
    }
}

core_MY_Controller.php

<?php

class MY_Controller extends CI_Controller {

    protected $layout_view = 'application';
    protected $content_view = '';
    protected $view_data = array();

    public function _output($output)
    {
        if ($this->content_view !== FALSE && empty($this->content_view)) ? $this->content_view = $this->router->class . '/' . $this->router->method;
        $yield = file_exists(APPPATH . 'views/' . $this->content_view . EXT) ? $this->load->view($this->content_view, $this->view_data, TRUE) : FALSE;
        
        if ($this->layout_view)
            echo $this->load->view('layouts/' . $this->layout_view, array('yield' => $yield), TRUE);
        else
            echo $yield;
    }
}