CakePHP code with many bugs

<!-- User model -->
<?php

class User extends AppModel {
    var $name = 'User';

    var $belongsTo = array (
        'Group'
    );

    var $hasMany = array (
        'UserLog',
        'WorkLog'
    );

    var $actAs = array (
        'Acl' => array ('type' => 'requester')
    );

    function parentNode () {
        if (!$this->id && empty ($this->data)) {
            return null;
        }

        if (isset ($this->data['User']['group_id'])) {
            $groupId = $this->data['User']['group_id'];
        } else {
            $groupId = $this->field ('group_id');
        }

        if (!$groupId) {
            return null;
        } else {
            return array (
                'Group' => array ('id' => $groupId)
            );
        }
    }
}

?>

<!-- Group Model -->

<?php

class Group extends AppModel {
    var $name = 'Group';

    var $hasMany = array (
        'User'
    );

    var $actAs = array (
        'Acl' => array ('type' => 'requester')
    );

    function parentNode () {
        return null;
    }
}

?>

<!-- Users Controller -->

<?php

class UsersController extends AppController {
    var $name = 'Users';

    function index() {
        $this->User->recursive = 0;
        $this->set('users', $this->paginate());
    }

    function beforeFilter () {
        parent::beforeFilter();

        /* FIXME: Temporal code */
        $this->Auth->allow (array ('*'));
    }

    public function login () {

    }

    public function logout () {
        $this->Auth->logout();
        $this->redirect('/');
    }

    public function dashboard () {

    }

    function view($id = null) {
        if (!$id) {
            $this->Session->setFlash(__('Invalid user', true));
            $this->redirect(array('action' => 'index'));
        }
        $this->set('user', $this->User->read(null, $id));
    }

    function add() {
        if (!empty($this->data)) {
            $this->User->create();
            if ($this->User->save($this->data)) {
                $this->Session->setFlash(__('The user has been saved', true));
                $this->redirect(array('action' => 'index'));
            } else {
                $this->Session->setFlash(__('The user could not be saved. Please, try again.', true));
            }
        }
        $groups = $this->User->Group->find('list');
        $this->set(compact('groups'));
    }

    function edit($id = null) {
        if (!$id && empty($this->data)) {
            $this->Session->setFlash(__('Invalid user', true));
            $this->redirect(array('action' => 'index'));
        }
        if (!empty($this->data)) {
            if ($this->User->save($this->data)) {
                $this->Session->setFlash(__('The user has been saved', true));
                $this->redirect(array('action' => 'index'));
            } else {
                $this->Session->setFlash(__('The user could not be saved. Please, try again.', true));
            }
        }
        if (empty($this->data)) {
            $this->data = $this->User->read(null, $id);
        }
        $groups = $this->User->Group->find('list');
        $this->set(compact('groups'));
    }

    function delete($id = null) {
        if (!$id) {
            $this->Session->setFlash(__('Invalid id for user', true));
            $this->redirect(array('action'=>'index'));
        }
        if ($this->User->delete($id)) {
            $this->Session->setFlash(__('User deleted', true));
            $this->redirect(array('action'=>'index'));
        }
        $this->Session->setFlash(__('User was not deleted', true));
        $this->redirect(array('action' => 'index'));
    }
}

<!-- Groups Controller -->
<?php

class GroupsController extends AppController {
    var $name = 'Groups';

    function beforeFilter () {
        parent::beforeFilter();

        /* FIXME: Temporal code */
        $this->Auth->allow (array ('*'));
    }

    function index() {
        $this->Group->recursive = 0;
        $this->set('groups', $this->paginate());
    }

    function view($id = null) {
        if (!$id) {
            $this->Session->setFlash(__('Invalid group', true));
            $this->redirect(array('action' => 'index'));
        }
        $this->set('group', $this->Group->read(null, $id));
    }

    function add() {
        if (!empty($this->data)) {
            $this->Group->create();
            if ($this->Group->save($this->data)) {
                $this->Session->setFlash(__('The group has been saved', true));
                $this->redirect(array('action' => 'index'));
            } else {
                $this->Session->setFlash(__('The group could not be saved. Please, try again.', true));
            }
        }
    }

    function edit($id = null) {
        if (!$id && empty($this->data)) {
            $this->Session->setFlash(__('Invalid group', true));
            $this->redirect(array('action' => 'index'));
        }
        if (!empty($this->data)) {
            if ($this->Group->save($this->data)) {
                $this->Session->setFlash(__('The group has been saved', true));
                $this->redirect(array('action' => 'index'));
            } else {
                $this->Session->setFlash(__('The group could not be saved. Please, try again.', true));
            }
        }
        if (empty($this->data)) {
            $this->data = $this->Group->read(null, $id);
        }
    }

    function delete($id = null) {
        if (!$id) {
            $this->Session->setFlash(__('Invalid id for group', true));
            $this->redirect(array('action'=>'index'));
        }
        if ($this->Group->delete($id)) {
            $this->Session->setFlash(__('Group deleted', true));
            $this->redirect(array('action'=>'index'));
        }
        $this->Session->setFlash(__('Group was not deleted', true));
        $this->redirect(array('action' => 'index'));
    }
}

?>

<!-- App Controller -->
<?php

class AppController extends Controller {
    var $components = array ('Acl', 'Auth', 'Session');
    var $helpers = array ('Html', 'Form', 'Session');

    function beforeFilter () {
        $this->Auth->loginAction = array (
            'controller' => 'users',
            'action' => 'login'
        );

        $this->Auth->autoRedirect = array (
            'controller' => 'users',
            'action' => 'dashboard'
        );

        $this->Auth->loginRedirect = array (
            'controller' => 'users',
            'action' => 'dashboard'
        );

        $this->Auth->logoutRedirect = array (
            'controller' => 'users',
            'action' => 'logout'
        );

        $this->actionPath = 'controllers/';

        /* FIXME: important read about ACL ( http://api.cakephp.org/class/auth-component )  */
        $this->authorize = 'actions';
    }
}