//application.php
<?php
class MyApp
{
function getUser()
{
   $userId = $session['hedehodo']
   if(user giris yaptiysa)
   {
       $user = new User($id);
   }
   else
   {
       $user = new User();
       $user->guest = true;
   }
   return $user;
}

function checkLogin($username,$password)
{
    $user = User::getUserByUserName($username);
    if($user->password == $password)
    {
      $session['hedehodo' = bilmemne
      return true;
    }
    else
    {
       return false;
    }
}

?>