3.6. Observer¶

 1<?php
 2
 3class NewsPublisher implements SplSubject
 4{
 5    private SplObjectStorage $observers;
 6    private array $articles;
 7
 8    public function __construct()
 9    {
10        $this->observers = new SplObjectStorage();
11        $this->articles = array();
12    }
13
14    public function attach(SplObserver $observer)
15    {
16        $this->observers->attach($observer);
17    }
18
19    public function detach(SplObserver $observer)
20    {
21        $this->observers->detach($observer);
22    }
23
24    public function notify()
25    {
26        foreach ($this->observers as $observer) {
27            $observer->update($this);
28        }
29    }
30
31    public function publishArticle($title, $content)
32    {
33        $this->articles[] = array(
34            'title' => $title,
35            'content' => $content,
36        );
37
38        $this->notify();
39    }
40
41    public function getArticles(): array
42    {
43        return $this->articles;
44    }
45}

 1<?php
 2
 3// Define the observer interface
 4class NewsSubscriber implements SplObserver
 5{
 6    private string $name;
 7
 8    public function __construct(string $name)
 9    {
10        $this->name = $name;
11    }
12
13    public function update(SplSubject $subject)
14    {
15        $articles = $subject->getArticles();
16        echo "Hello {$this->name}, the following articles have been published:\n";
17        foreach ($articles as $article) {
18            echo "- {$article['title']} : {$article['content']}\n";
19        }
20        echo "\n";
21    }
22}

 1<?php
 2
 3// Create the news publisher and attach subscribers
 4$publisher = new NewsPublisher();
 5$subscriber1 = new NewsSubscriber('Saleh');
 6$subscriber2 = new NewsSubscriber('Mina');
 7
 8$publisher->attach($subscriber1);
 9$publisher->attach($subscriber2);
10
11// Publish new articles
12$publisher->publishArticle('New article 1', 'Content for new article 1');
13$publisher->publishArticle('New article 2', 'Content for new article 2');
14
15// Notify all subscribers
16$publisher->notify();
17
18// Detach a subscriber
19$publisher->detach($subscriber2);
20
21// Publish another article
22$publisher->publishArticle('New article 3', 'Content for new article 3');
23
24// Notify all subscribers
25$publisher->notify();