Observer Pattern

index.php

<?php

interface Subject {

    public function attach(Observable $observable);

    public function detach(Observable $observable);

    public function next($value);
}

interface Observable {

    public function __construct($eventName);

    public function subscribe($value);

    public function eventName();

}

class Notify implements Subject {

    /**
     * @var Observable[]
     */
    protected $observables;

    public function attach(Observable $observable)
    {
        $this->observables[$observable->eventName()] = $observable;
    }

    public function detach(Observable $observable)
    {
        unset($this->observables[$observable->eventName()]);
    }

    public function next($value)
    {
        foreach ($this->observables as $observable) {
            $observable->subscribe($value);
        }
    }

}

class Email implements Observable {

    private $eventName;

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


    public function subscribe($value)
    {
        var_dump('SEND EMAIL ' . $value);
    }

    public function eventName()
    {
        return $this->eventName;
    }


}

class Pager implements  Observable {

    private $eventName;

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

    public function subscribe($value)
    {
        var_dump('PAGE USER ' . $value);
    }

    public function eventName()
    {
        return $this->eventName;
    }


}

$notify = new Notify();
$notify->attach(new Email('send_email_to_admin'));
$notify->attach(new Pager('send_page_duty'));
$notify->attach(new Email('send_email_to_cto'));

$notify->next('server down');