如何使用codeigniter 3在hooks文件夹中调用库？

I have a problem I tried this codes:

• enabled hooks in application/config/config.php

  $config['enable_hooks'] = TRUE;
  

• added library in applciation/config/autoload.php

  $autoload['libraries'] = array('smarty','session');
  

• code in application/config/hooks.php:

  $hook['post_controller_constructor'][] = array(
      'class'    => 'App_auth',
      'function' => 'index',
      'filename' => 'App_auth.php',
      'filepath' => 'controllers',
      'params'   => ''
  );
  

• code in application/controller/App_auth.php :

  class Auth_module
  {
      private $CI;
  
      function Auth_module()
      {
          $this->CI = &get_instance();
      }
  
      function index()
      {
          echo'aaaaaaaa';exit(0);
          if ($this->CI->session->userdata('user_id') == "" )  // If no session found redirect to login page.
          {
              redirect(site_url('login'));
          }
      }
  }
  

• sample code in application/libraries/Session.php:

  Please check this site for the codehttp://codeigniter.com/user_guide/libraries/sessions.html
  

• Replaced function userdata($item) with this code:

  function userdata($item)
  {
      echo'bbbb';exit;
      return ( ! isset($this->userdata[$item])) ? FALSE : $this->userdata[$item];
  }
  

I don't have any idea what could be the solution as I already other codes. Please enlighten me with this. THANKS! :)

Why is that echo'aaaa'; and echo 'bbbb'; are not showing? Also is there wrong with my code?

enable hooks in config

$config[‘enable_hooks’] = TRUE;

Codeigniter Hooks tutorials

Your Auth_module should contain

function Auth_module()
{
$this->CI = &get_instance();
}