Zend Framework issue: Zend_Form class not included

The other day I decided to master the Zend Framework and found a screencast http://vimeo.com/12704093,
installed, but I can’t figure out why the Zend_Form class is not included!

Can’t create form.

//    UsersController
class UsersController extends Zend_Controller_Action
{
    public function indexAction()
    {
      $this->view->title= ' .';
      $this->view->headTitle($this->view->title,'PREPEND');
    }
    public function addAction()
    {
      $this->view->title= '  .';
      $this->view->headTitle($this->view->title,'PREPEND');
      //     Form_User()
      $form =  new Form_User();
      $this->view->form = $form;
    }
    public function deleteAction()
    {
    }
    public function viewAction()
    {
      $this->view->title= '  .';
      $this->view->headTitle($this->view->title,'PREPEND');
    }
    public function editAction()
    {
      $this->view->title= '  .';
      $this->view->headTitle($this->view->title,'PREPEND');
    }
}
//    User
class Form_User extends Zend_Form
{
    public function _construct()
    {
        $this->setName('form_user');
        parent::__construct();
        $username = new Zend_Form_Element_Text('username');        
        $password = new Zend_Form_Element_Password('password');        
        $email = new Zend_Form_Element_Text('email');        
        $submit = new Zend_Form_Element_submit('submit');        
        $this->addElements(array($username,$password,$email,$submit));
    }
}

Answer 1, authority 100%

Your form class should be named Application_Form_User. Then ZF will look for it in “application/forms/User.php”.

UPD:And initialize the form not in the constructor, but in the init()

method

class Application_Form_User extends Zend_Form
{
    public function init()
    {
        $this->setName('form_user');
        $username = new Zend_Form_Element_Text('username');        
        $password = new Zend_Form_Element_Password('password');        
        $email = new Zend_Form_Element_Text('email');        
        $submit = new Zend_Form_Element_submit('submit');        
        $this->addElements(array($username,$password,$email,$submit));
    }
}

Answer 2

Instead of $form = new Form_User();
try using the full record.
$form = new Application_Form_User();