What the bug in this case ?

[eluser]Tống Kiện Phi[/eluser]
In the autoload config:

Code:

$autoload['helper'] = array('url');

In the core folder, i created MY_Controller:

Code:

class MY_Controller extends CI_Controller {
    
    public $_data = array();
    
    public function __construct()
    {
        $this->_data['image_path'] = base_url() . 'public/images/';
    }
}

When i run website, it's display error:

Fatal error: Call to undefined function base_url() in D:\UniServer\www\note\application\core\MY_Controller.php on line 17

I don't know why