<?php
require_once 'Observer.php';

abstract class Subject {
  protected $observers = array();

  public function attach(Observer $observer) {
      $this->observers[] = $observer;
  }

  public function detach(Observer $observer) {
    for ($i = 0; $i < sizeof($this->observers); $i++) {
      if ($this->observers[$i] === $observer) {
        unset($this->observers[$i]);
      }
    }
  }

  protected function notify() {
    for ($i = 0; $i < sizeof($this->observers); $i++) {
      $this->observers[$i]->update();
    }
  }

  public abstract function getState();
}
?>