$adminSession = new Zend_Session_Namespace('Admin');
$this->access = new Application_Model_accessControl(); // access control
 
// logged in user
$loginMsg = 'Please login';
$loginForm = new Zend_Form;
$loginForm
	->setMethod('post')
	->setAttrib('id','login')
	->addElement('text','user',array('label'=>'Username','required'=>true))
	->addElement('password','pass',array('label'=>'Password','required'=>true))
	->addElement('submit','Login');
 
if ($this->getRequest()->isPost() && $loginForm->isValid($_POST)){
	$session = $this->access->validateUser(
		$loginForm->getValue('user'), 
		$loginForm->getValue('pass')
		);
 
	if ($session){
		$adminSession->loggedInSession = $session;
		$adminSession->loggedInUser = $loginForm->getValue('user');
	}
 
	$loginMsg='Access denied';
} 			
 
if (!$this->access->sessionIsValid($adminSession->loggedInSession) || !$adminSession->loggedInUser){
       	$this->view->header=$loginMsg;			
	$this->view->content = $loginForm;
	$this->render('login');  
} else {
	// renew session, will always be the "Now" session, but three are provided, see the model 
	$adminSession->loggedInSession = $this->access->getValidSession();
    	$this->view->userIdent = $adminSession->loggedInUser;
}

<?php
 
class Application_Model_accessControl
{
 
 
	public function __construct(){
 
		// set users, password is the key, because this is less likely to be duplicated
        $this->setUsers(
        	array(
				'password1'=>'admin',
				'password2'=>'admin'
				)
       		);
        // salt for session key
		$this->setSalt('MySaltGoesHere1234');
	}
 
	public function validateUser($username, $password){
 
		/*
		 * return session if correct, null otherwise
		 */
 
		$users = $this->getUsers();
 
		if (isset($users[$password]) && $users[$password]==$username){
			return $this->getValidSession();
		}
	}
	public function sessionIsValid($session,$debug=false){
 
		$validSessions = $this->getValidSessions();
		if ($debug){
			echo "MY KEY: $session<br >KEYS: ".print_r($validSessions,true);
		}
		return in_array($session, $validSessions) ? true : false;
	}
 
	public function getValidSessions(){
 
		$sessions = array(
			$this->getValidSession('past'),
			$this->getValidSession('now'),
			$this->getValidSession('future')
			);
 
		return $sessions;
	}
	public function getValidSession($for='now'){
 
		/*
		 * Three sessions are provided,
		 * 
		 * past, now and present
		 * 
		 * past, person logs in at 11:59 spends ten minutes editing, clicks save at 12:09, past would be the valid session
		 * now, person is logged in during 11:00 - 11:59
		 * future, is provided encase of time travel, or if the british summer time kicks in while editing, unlikely but more is better than not enough...
		 */
 
		$hour = intval(date('H'));
 
		switch($for){
			case 'past' : 
				$validSession = ($hour-1) < 0 ? 23 : $hour-1;
			break;
			case 'now' : default:
				$validSession = $hour;
			break;
			case 'future' : 
				$validSession = ($hour+1) > 23 ? 0 : $hour+1;
			break;
 
		}
 
		/*
		 * obsfucation
		 */
		// firstly grab specific details to stop session hijacking 
		$ip = $_SERVER['REMOTE_ADDR'];
		$browser = $_SERVER['HTTP_USER_AGENT'];
		// then mix it up and md5 it
		$validSession = $ip.$validSession.$this->getSalt().$browser;
 
		if (!getenv('APPLICATION_ENV')){
			$validSession = md5($validSession);
		}
 
		return $validSession;
	}
 
	public function setUsers($users){
		$this->users = $users;
	}
	public function getUsers(){
		return $this->users;
	}
	public function setSalt($salt){
		$this->salt = $salt;
	}
	public function getSalt(){
		return $this->salt;
	}
 
 
}

<?php echo "<h2>{$this->header}</h2>";  ?>
<?php echo $this->content;  ?>