@maurice; Check this example of RegisterController.php with activateAction

RegisterController.php

<?php 
class RegisterController extends Zend_Controller_Action {
	
	public function init ()
	{
		$this->view->title = 'Register';
		$this->view->menu = 'home';
	}

	public function indexAction() {
		$formRegister = new Application_Forms_Register();
		
		if ($this->_request->isPost()) {
			if ($formRegister->isValid($this->_request->getPost())) {
				$data = $formRegister->getValues();
			
				// insert company
				$company = new Application_Model_Company();
				$id_company = $company->insert(array(
					'name' => $data['company'],
					'id_group' => 3
				));
				
				// insert default company in addressbook
				$address = new Application_Model_Addressbook();
				$address->insert(array(
					'name' => $data['company'],
					'id_company' => $id_company
				),true);
				
				$hash = md5(mt_rand().uniqid());
				
				// insert user
				$user = new Application_Model_User();
				$user->insert(array(
					'name' => $data['name'],
					'email' => $data['email'],
					'password' => md5(SALT.$data['password']),
					'active' => '0',
					'language' => 'NL',
					'id_company' => $id_company,
					'hash_activate' => $hash
				));
				
				// send e-mail to user (with activation link)
				$url = 'http://'.$_SERVER['SERVER_NAME'].'/register/activate/?hash='.$hash;
				
				$html = new Zend_View();
				$html->setScriptPath(APPLICATION_PATH. '/views/scripts/register/');
				$html->assign("hash",$url);
				$html->assign("name",$data['name']);
				
				$body = $html->render('email.phtml');
				
				$mail = new Zend_Mail();
				$mail->setFrom('no-reply@application.nl', 'Application')
					->addTo($data['email'], $data['email'])
					->setSubject('Welkom bij Application')
					->setBodyHtml($body)
					->send();
				
				$this->render("thanks");
			} else {
				$errors = $formRegister->getErrors();
				$this->view->errors = $errors;
			}
		}
		
		$this->view->form = $formRegister;
		
	}
	
	public function activateAction() {
		// activate account + automatic login 
		Zend_Auth::getInstance()->clearIdentity();
		
		$hash = $this->_getParam("hash","xxx");
		$model = new Application_Model_User();
		$user = $model->getByHash($hash);
		
		if(isset($user) && count($user) > 0) {
			
			$dbAdapter = Zend_Db_Table::getDefaultAdapter();
			$authAdapter = new Zend_Auth_Adapter_DbTable($dbAdapter);
			
			$authAdapter->setTableName('user')
				->setIdentityColumn('email')
				->setCredentialColumn('hash_activate');
			
			$authAdapter->setIdentity($user['email'])
				->setCredential($hash);
			
			$auth = Zend_Auth::getInstance();
			$result = $auth->authenticate($authAdapter);

			if($result->isValid()) {
				$userInfo = $authAdapter->getResultRowObject(null, 'password');
        		
				$user = new Application_Model_User();
				$user->update(array(
					'id'=> $userInfo->id,
					'active' => 1,
					'hash_activate' => null,
					'lastlogin' => new Zend_Db_Expr('NOW()')
				));
        				
				$company = new Application_Model_Company();
				$companyInfo = $company->findById($userInfo->id_company);
				$userInfo->company = $companyInfo[0];
        			
				$authStorage = $auth->getStorage();
				$authStorage->write($userInfo);
				
				$this->_redirect('/');
			}
			
		} else {
			// no valid activation link, go to normal view modus...
		}
		
	}
}