SplObserver 和 SplSubject 接口实现观察者模式

<?php

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

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

    public function detach(SplObserver $observer) {
        foreach ($this->observers as $key => $obs) {
            if ($obs === $observer) {
                unset($this->observers[$key]);
            }
        }
    }

    public function notify() {
        foreach ($this->observers as $observer) {
            $observer->update($this);
        }
    }

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

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

class Observer implements SplObserver {
    private $name;

    public function __construct($name) {
        $this->name = $name;
    }

    public function update(SplSubject $subject) {
        echo "观察者==》{$this->name} 开始执行事件: " . $subject->getState() . "\n";
    }
}

// 创建主题
$subject = new Subject();

// 创建观察者
$observer1 = new Observer("观察者 1");
$observer2 = new Observer("观察者 2");

// 将观察者添加到主题
$subject->attach($observer1);
$subject->attach($observer2);

// 改变状态
$subject->setState("事件");

输出