How can the ObserverPattern be effectively used in PHP for website projects?

Issue: The ObserverPattern can be effectively used in PHP for website projects to implement a system where an object (subject) maintains a list of dependents (observers) that are notified of any state changes and can react accordingly. PHP Code Snippet: 

<?php

// Subject interface
interface Subject {
    public function attach(Observer $observer);
    public function detach(Observer $observer);
    public function notify();
}

// Observer interface
interface Observer {
    public function update();
}

// Concrete subject
class ConcreteSubject implements Subject {
    private $observers = [];

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

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

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

// Concrete observer
class ConcreteObserver implements Observer {
    public function update() {
        echo "Observer notified of state change\n";
    }
}

// Implementation
$subject = new ConcreteSubject();
$observer1 = new ConcreteObserver();
$observer2 = new ConcreteObserver();

$subject->attach($observer1);
$subject->attach($observer2);

$subject->notify();

?>

Keywords

ObserverPattern PHP website projects design pattern event-driven architecture

Related Questions