[Design Pattern] (Observer) - Newspaper and Reader

[Design Pattern] (Observer) - Newspaper and Reader

$newspaper = new Newspaper('Newyork Times');

$allen = new Reader('Allen');
$jim = new Reader('Jim');
$linda = new Reader('Linda');

//add reader
$newspaper->attach($allen);
$newspaper->attach($jim);
$newspaper->attach($linda);

//remove reader
//$newspaper->detach($linda);

//set break outs
$newspaper->breakOutNews('USA break down!');

//=====output======
//Allen is reading breakout news USA break down! (Newyork Times)
//Jim is reading breakout news USA break down! (Newyork Times)

Newspaper.php

class Newspaper implements SplSubject
{
   private $name;
   private $observers = [];
   private $content;

   public function __construct($name)
   {
       $this->name = $name;
   }

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

   public function detach(SplObserver $observer)
   {
       $key = array_search($observer, $this->observers, true);
       if ($key) {
           unset($this->observers[$key]);
       }
   }

   public function notify()
   {
       foreach ($this->observers as $value) {
           $value->update($this);
       }
   }


   public function breakOutNews($content)
   {
       $this->content = $content;
       $this->notify();
   }

   public function getContent()
   {
       return $this->content . " ({$this->name})";
   }
}

Reader.php

class Reader implements SplObserver
{
   private $name;

   public function __construct($name)
   {
       $this->name = $name;
   }

   public function update(SplSubject $subject)
   {
       echo $this->name . ' is reading breakout news <b>' . $subject->getContent() . '</b>' . PHP_EOL;
   }
}