Zend login form in the header

Finally I have managed to solve this task and works as expected. Of course, it can be extended. Here it is a simple way.

application.ini

resources.frontController.actionhelperpaths.Application_Controller_Helper = APPLICATION_PATH "/controllers/helpers"

Bootstrap.php

protected function _initMyActionHelpers()
{
    $this->bootstrap('frontController');
    $login = Zend_Controller_Action_HelperBroker::getStaticHelper('Login');
    Zend_Controller_Action_HelperBroker::addHelper($login);
}

application/forms/Login.php

class Application_Form_Login extends Zend_Form
{
    public function init()
    {
            $this->addElement('text', 'username', array(
            'placeholder' => 'Userame',
            'required' => true,
            'validators' => array(
            array('StringLength', false, array('max'=>75))
            )
            ));
            $this->addElement('password', 'password', array(
            'placeholder' => 'Password',
            'required' => true,
            'validators' => array(
            array('StringLength', false, array('max'=>150))
            )
            ));
            $this->addElement('submit', 'submitlogin', array(
            'label' => 'Login'
            ));
    }
}

application/forms/Logout.php

class Application_Form_Logout extends Zend_Form
{
    public function init()
    {
        $this->addElement('submit', 'submitlogout', array(
        'label' => 'Logout'
        ));
    }
}

application/controllers/helpers/Login.php

class Application_Controller_Helper_Login extends Zend_Controller_Action_Helper_Abstract
{
    public function preDispatch()
    {
        $sessionUser = new Zend_Session_Namespace('user');
        $request = $this->getActionController()->getRequest();
        if(!isset($sessionUser->username)){
            $form = new Application_Form_Login();
            if($request->isPost() && $request->getPost('submitlogin')) {
                if($form->isValid($request->getPost())) {
                    $data = $form->getValues();
                    $sessionUser = new Zend_Session_Namespace('user');
                    $sessionUser->username = $data['username'];
                }
            }            
        } else {
            if($request->isPost() && $request->getPost('submitlogout')) {
                Zend_Session::namespaceUnset('user');
            }
        }
    }
}

application/views/helpers/Login.php

class Zend_View_Helper_Login extends Zend_View_Helper_Abstract
{
    public function Login()
    {
        $html = '';
        $sessionUser = new Zend_Session_Namespace('user');
        if(isset($sessionUser->username)) {
            $html = '<p>Welcome, ' . $sessionUser->username . '.</p>';
            $logout_form = new Application_Form_Logout();
            $html .= $logout_form;
        } else {
            $login_form = new Application_Form_Login();
            $html .= $login_form;
        }
        return $html;
    }
}

layout.phtml

<div id="header"><?php echo $this->Login($this->Login); ?></div>