Implementation Of Oberver Design Pattern in PHP (Practical Example)

<?php

/*
 *
 * @Author: Zuhair Mirza
 * @Implementation Of Oberver Design Pattern in PHP (Practical Example)
 * @Date : 15-June-2015
 * @Defination  :  An object is made observable by adding a method that allows
 * another object, the observer to get registered. If the observable object gets changed,
 * it sends a message to the objects which are registered as observers:
 *
 */

interface Observer {

    function onChanged($sender, $args);
}

interface Observable {

    function addObserver($observer);
}

class CustomerList implements Observable {

    private $_observers = array();

    public function addCustomer($name) {
        foreach ($this->_observers as $obs)
            $obs->onChanged($this, $name);
    }

    public function addObserver($observer) {
        $this->_observers [] = $observer;
    }

    public function getObserver() {

        return $this->_observers;
    }

}

class CustomerListLogger implements Observer {

    public function onChanged($sender, $args) {
        echo( "'$args' Customer has been added to the list \n" );
    }

}

$ul = new CustomerList();

$ul->addObserver(new CustomerListLogger());
$ul->addCustomer("Zuhair");   // Output : 'Zuhair' Customer has been added to the list
$ul->addCustomer("Mirza");    // Output : 'Mirza'  Customer has been added to the list

var_dump($ul->getObserver()); // Output :  array(1) { [0]=> object(CustomerListLogger)#2 (0) { } }