php观察者模式(observer pattern)

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<?php
/*
The observer pattern implements a one-too-many dependency between objects. The
object that holds the list of dependencies is called subject, while the dependents are
called observers. When the subject object changes state, all of the dependents are
notified and updated automatically.
*/

class Customer implements \SplSubject {
    protected $data = array();
    protected $observers = array();

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

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

    public function notify() {
        foreach ($this->observers as $observer) {
            $observer->update($this);
            echo 'Customer_observer updated.<br/>';
        }
    }

    public function __set($name, $value) {
        $this->data[$name] = $value;
        $this->notify();
    }
}

class CustomerObserver implements \SplObserver {
    public function update(\SplSubject $subject) {
        echo "CustomerObserver_update.<br/>";
    }
}

$user = new Customer;
$customerObserver = new CustomerObserver();
$user->attach($customerObserver);

$user->name = 'John Doe';
$user->email = 'john.doe@fake.com';

?>