观察者模式

<?php

class Subject implements SplSubject
{
    private $observers = [];
    private $stateNow;

    /**
     * Attach an SplObserver
     * @param SplObserver $observer
     */
    public function attach(SplObserver $observer)
    {
        // TODO: Implement attach() method.
        $this->observers[] = $observer;
    }

    /**
     * Detach an observer
     * @param SplObserver $observer
     */
    public function detach(SplObserver $observer)
    {
        // TODO: Implement detach() method.
        $key = array_search($observer, $this->observers);
        if ($key !== false) {
            unset($this->observers[$key]);
        }
    }

    /**
     * Notify an observer
     */
    public function notify()
    {
        // TODO: Implement notify() method.
        foreach ($this->observers as $observer) {
            $observer->update($this);
        }
    }

    public function setState($state)
    {
        $this->stateNow = $state;
        $this->notify();
    }

    public function getState()
    {
        return $this->stateNow;
    }
}


class EmailObserver implements SplObserver
{
    /**
     * Receive update from subject
     * @param SplSubject $subject
     */
    public function update(SplSubject $subject)
    {
        // TODO: Implement update() method.
        echo $subject->getState() . ‘,发送邮件‘ . PHP_EOL;
    }
}

class SmsObserver implements SplObserver
{
    /**
     * Receive update from subject
     * @param SplSubject $subject
     */
    public function update(SplSubject $subject)
    {
        // TODO: Implement update() method.
        echo $subject->getState() . ‘,发送短信‘ . PHP_EOL;
    }
}

// run
$emailObserver = new EmailObserver();
$smsObserver = new SmsObserver();

$subject = new Subject();
$subject->attach($emailObserver);
$subject->attach($smsObserver);
$subject->setState(‘用户修改密码‘);