<?php

class Base
{
  /** @var Database */
  var $Database;
  /** @var System */
  var $System;

  function __construct($System)
  {
    $this->System = &$System;
    $this->Database = &$System->Database;    
  }
}

class Model extends Base
{
  
}

class View extends Base
{
  
}

class Controller extends Base
{
  
}