在例子中，创建两个类,一个是通用的Product类,它封装了一个产品和产品的属性，别一个是购物车的Cart类　

Product类(Product.php)

class Product{
   protected $_partNumber,$_description,$_price;
   
   public function __construct($parNumber,$description,$price){
   	  $this->_partNumber=$parNumber;
   	  $this->_description=$description;
   	  $this->_price=$price;
   	
   }
   
   public function getPartNumber(){
   	return $this->_partNumber;
   }
   
   public function getDescription(){
   	return $this->_description;
   }
   
   public function getPrice(){
   	return $this->_price;
   }
}

Cart对象(Cart.php)

require_once ('Product.php');

class Cart extends ArrayObject{
	
	protected $_products;
	
	public function __construct(){
		$this->_products=array();
		parent::__construct($this->_products);
	}
	
	public function getCarTotal(){
		for(
		  $i=$sum=0,$cnt=count($this);
		  $i<$cnt;
		  $sum+=$this[$i++]->getPrice()
		);
		return $sum;
	}
	
}

调用方法,

$cart=new Cart();
$cart[]=new Product('00231-A','Description',1.99);
$cart[]=new Product('00231-B','B',1.99);
echo $cart->getCarTotal();

getCarTotal可以统计总价

得值

3.98