Stuff

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

if ( ! class_exists('Category_group'))
{
     require_once(APPPATH.'libraries/category_group'.EXT);
}

$obj =& get_instance();
$obj->category_group = new Category_group($id);
$obj->ci_is_loaded[] = 'category_group';

?>