设计模式之观察者模式

<?php
function buy($user)
{
    echo "buy success\n";
    return true;
}

class User
{
    private $_observers = array();
 
    public function register($sub)
    { /*  注册观察者 */
        $this->_observers[] = $sub;
    }

    public function trigger()
    {  /*  外部统一访问    */
        if(!empty($this->_observers)){
            foreach($this->_observers as $observer){
                $observer->update();
            }
        }
    }
}
 
/**
 * 观察者要实现的接口
 */
interface Observerable{
    public function update();
}
 
class Sms implements Observerable{
    public function update(){
        echo "Sms notify\n";
    }
}

class Email implements Observerable {
    public function update() {
        echo ‘Email notify‘;
    }
}


$u = new User();
$u->register(new Sms());
$u->register(new Email());
if (buy($u)) {
    $u->trigger();
}