PHP 데코레이터 패턴의 구현 및 사용법에 대한 자세한 설명

<?php
//装饰器模式-在不改变原有类的结构上，对类的功能那个作补充
//武器基类
abstract class Weapon{
  abstract public function descriptions();
  abstract public function cost();
}
//剑类
class Glave extends Weapon{
  public function descriptions(){
    return &#39;Glave&#39;;
  }
  public function cost(){
    return "100";
  }
}
//匕首类
class Knife extends Weapon{
  public function descriptions(){
    return __CLASS__;
  }
  public function cost(){
    return "80";
  }
}
//斧类
class Axe extends Weapon{
  public function descriptions(){
    return __CLASS__;
  }
  public function cost(){
    return "200";
  }
}
//属性类
class Property extends Weapon{
  protected $_weapon = null;
  protected $_price = 0;
  protected $_descriptions = &#39;&#39;;
  public function __construct(Weapon $weapon){
    $this->_weapon = $weapon;
  }
  public function cost(){
    return   $this->_weapon->cost() + $this->_price;
  }
  public function descriptions(){
    return $this->_weapon->descriptions().$this->_descriptions;
  }
}
//力量属性
class Strength extends Property{
  protected $_price = 30;
  protected $_descriptions = &#39;+ Strength&#39;;
}
//敏捷属性
class Agility extends Property{
  protected $_price = 50;
  protected $_descriptions = &#39;+ Agility&#39;;
}
//智力属性
class Intellect extends Property{
  protected $_price = 20;
  protected $_descriptions = &#39;+ Intellect&#39;;
}
$weapon = new Agility(new Strength(new Strength(new Glave())));
echo $weapon->cost();
echo $weapon->descriptions();