Duplicate AppController cakephp - php

Question

for my site I need to have two different auth session because one login is for admin section (like worpdress admin "wp-admi" access), and one login is for account login into the site.
So I have thought to duplicate AppController with AppAdminController but I retrieve some error.
This is my AppAdminController
App::uses('Controller', 'Controller');
class AppAdminController extends Controller {
public $helpers = array('Html', 'Form', 'Session'); //'DebugKit.Toolbar'
public $components = array(
'Session',
'Auth' => array(
'loginRedirect' => array('controller' => 'admin', 'action' => 'index'),
'logoutRedirect' => array('controller' => 'admin', 'action' => 'index'),
'authError' => 'Questa risorsa non sembra appartenere al tuo account, oppure non hai eseguito l\'accesso',
'autoRedirect' => false,
'authorize' => array(
'Controller',
'Actions' => array(
'actionPath' => 'controllers'
)
),
'authenticate' => array(
'Form' => array(
'fields' => array('username' => 'username')
)
)
)
);
public function afterFilter () {
}
public function beforeFilter () {
}
}
and I use it into AdminController:
App::uses('AppAdminController', 'Controller');
App::uses('AppController', 'Controller');
class AdminController extends AppAdminController {
public $name = 'Admin';
public $scaffold;
public $uses = 'users';
public $useDbConfig = 'admin';
public function beforeFilter () {
parent::beforeFilter();
$user_type = 'guest';
if($this->Session->read('is_logged')){
$auth_user = $this->Auth->user();
$user_type = $auth_user['group'];
}
}
}
I retrieve this error:
Call to a member function read() on a non-object
into this line:
if($this->Session->read('is_logged')){
How can I fix this?
Thanks