备忘录模式（Memento）

模式架构简单代码实现示例：

<?php
class Originator { // 发起人(Originator)角色
    private $_state;
    public function __construct() {
        $this->_state = '';
    }
    public function createMemento() { // 创建备忘录
        return new Memento($this->_state);
    }
    public function restoreMemento(Memento $memento) { // 将发起人恢复到备忘录对象记录的状态上
        $this->_state = $memento->getState();
    }
    public function setState($state) { $this->_state = $state; } 
    public function getState() { return $this->_state; }
    public function showState() {
        echo $this->_state;echo "<br>";
    }

}
class Memento { // 备忘录(Memento)角色 
    private $_state;
    public function __construct($state) {
        $this->setState($state);
    }
    public function getState() { return $this->_state; } 
    public function setState($state) { $this->_state = $state;}
}
class Caretaker { // 负责人(Caretaker)角色 
    private $_memento;
    public function getMemento() { return $this->_memento; } 
    public function setMemento(Memento $memento) { $this->_memento = $memento; }
}

// client
/* 创建目标对象 */
$org = new Originator();
$org->setState('open');
$org->showState();
/* 创建备忘 */
$memento = $org->createMemento();
/* 通过Caretaker保存此备忘 */
$caretaker = new Caretaker();
$caretaker->setMemento($memento);
/* 改变目标对象的状态 */
$org->setState('close');
$org->showState();
$org->restoreMemento($memento);
$org->showState();
/* 改变目标对象的状态 */
$org->setState('close');
$org->showState();
/* 还原操作 */
$org->restoreMemento($caretaker->getMemento());
$org->showState();