PHPで使うGoFパターン ひとり Advent Calendar - オブザーバー

<?php
interface ISubject {
  public function add ( $observer );
  public function remove ( $observer );
  public function notify ( $e );
}

interface IObserver {
  public function recieve ( $music );
}

class Radio implements ISubject {
  private $_List      = array ();
  private $_MusicList = array ();
  public function __construct () {
  }

  public function add ( $observer ) {
    if ( !( $observer instanceof IObserver ) )
      throw new Exception ( '無理じゃね?' );
    $this->_List[] = $observer;
  }

  public function remove ( $observer ) {
    $tmp = $this->_List;
    foreach ( $tmp as $obj ) {
      if ( $observer != $obj ) {
        $this->_List[] =$obj;
      }
    }
  }

  public function notify ( $e ) {
    foreach ( $this->_List as $obj ) {
      $obj->recieve ( $e );
    }
  }

  public function broadCast ( $music ) {
    $this->_MusicList[] = $music;
    $this->notify ( $music );
  }

  public function talk () {
    $this->notify ( 'DJの喋り' );
  }
}

class Listner implements IObserver {
  private $_Name = null;
  public function __construct ( $name ) {
    $this->_Name = $name;
  }

  public function recieve ( $music ) {
    print "$this->_Name さんが " . $music . " を聞きました\n";
  }
}

$radio = new Radio ();
$radio->add ( new Listner ( 'Larry' ) );
$radio->add ( new Listner ( 'Gates' ) );
$radio->add ( new Listner ( 'Jobs' ) );
$radio->broadCast ( 'Flim / Aphex Twin ' );
$radio->broadCast ( 'Journey to reedham / SquarePusher' );
$radio->talk ();