我如何在自己的库中使用mx_controller变量？

I am working on a project using HMVC codeigniter. i have my own library for layouts and my base controller named MY_Controller with this code:

class MY_Controller extends MX_Controller{
    public $layout='layout_name';
    public $theme='name';
    ...
    public function __construct(){
        parent::__construct();
        ...
        }
}

my problem is: when i use $this->CI=& get_instance(); in the library, the properties of my controller like $theme are unavailable. for example can not use $this->CI->theme; but in the controllers no problem exist and i can use $this->theme; anywhere. how can i make an instance contain my base controller variables in the library?

Solved. according to the CI documentation, i use second parameter of loading library and send my specified variables to library via array. in the mx_controller:

class MY_Controller extends MX_Controller{

    private $layout='default';
    private $theme='white';
    private $param=array();

    public function __construct(){
        parent::__construct();
        $this->param=array('layout'=>$this->layout,'theme'=>$this->theme);
        $this->load->library('lib',$this->param);
    }
}