<?php
 
 
$robots = new Observerable();
 
 
class KillingRobot implements SplObserver
 
{
 
    public function update(SplSubject $subject)
 
    {
 
        echo "kill all humans";
 
    }
 
}
 
 
class WashingRobot implements SplObserver
 
{
 
    public function update(SplSubject $subject)
 
    {
 
        echo "wash all humans";
 
    }
 
}
 
 
$killing_robot = new KillingRobot();
 
$washing_robot = new WashingRobot();
 
$robots->addObserver($killing_robot);
 
$robots->addObserver($washing_robot);
 
$robots->notify();
 
 
?>
 
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