php设计模式 Prototype (原型模式)代码

<?php 
/** 
* 原型模式 
* 
* 用原型实例指定创建对象的种类.并且通过拷贝这个原型来创建新的对象 
* 
*/ 
abstract class Prototype 
{ 
private $_id = null; 
public function __construct($id) 
{ 
$this->_id = $id; 
} 
public function getID() 
{ 
return $this->_id; 
} 
public function __clone() // magic function 
{ 
$this->_id += 1; 
} 
public function getClone() 
{ 
return clone $this; 
} 
} 
class ConcretePrototype extends Prototype 
{ 
} 
// 
$objPrototype = new ConcretePrototype(0); 
$objPrototype1 = clone $objPrototype; 
echo $objPrototype1->getID()."<br/>"; 
$objPrototype2 = $objPrototype; 
echo $objPrototype2->getID()."<br/>"; 
$objPrototype3 = $objPrototype->getClone(); 
echo $objPrototype3->getID()."<br/>";