购物车单例模式

<?php
/**
 * php 购物车类
 * 单例模式
*/
 class Cart{
 static protected $ins; //实例变量
 protected $item = array(); //放商品容器

 //禁止外部调用
 final protected function __construct(){
 }

 //禁止克隆
 final protected function __clone(){
 }

 //类内部实例化
 static protected function Getins(){
 if(!(self::$ins instanceof self)){
 self::$ins = new self();
 }

 return self::$ins;
 }

 //为了能使商品跨页面保存，把对象放入session里
 public function Getcat(){
 if(!($_SESSION['cat']) || !($_SESSION['cat'] instanceof self)){
 $_SESSION['cat'] = self::Getins();
 }

 return $_SESSION['cat'];
 }

 //入列时的检验，是否在$item里存在.
 public function Initem($goods_id){
 if($this->Gettype() == 0){
 return false;
 }
 if(!(array_key_exists($goods_id,$this->item))){
 return false;
 }else{
 return $this->item[$goods_id]['num']; //返回此商品个数
 }
 }

 //添加一个商品
 public function Additem($goods_id,$name,$num,$price){
 if($this->Initem($goods_id) != false){
 $this->item[$goods_id]['num'] += $num;
 return;
 }

 $this->item[$goods_id] = array(); //一个商品为一个数组
 $this->item[$goods_id]['num'] = $num; //这一个商品的购买数量
 $this->item[$goods_id]['name'] = $name; //商品名字
 $this->item[$goods_id]['price'] = $price; //商品单价
 }

 //减少一个商品
 public function Reduceitem($goods_id,$num){
 if($this->Initem($goods_id) == false){
 return;
 }
 if($num > $this->Getunm($goods_id)){
 unset($this->item[$goods_id]);
 }else{
 $this->item[$goods_id]['num'] -=$num;
 }
 }

 //去掉一个商品
 public function Delitem($goods_id){
 if($this->Initem($goods_id)){
 unset($this->item[$goods_id]);
 }
 }

 //返回购买商品列表
 public function Itemlist(){
 return $this->item;
 }

 //一共有多少种商品
 public function Gettype(){
 return count($this->item);
 }

 //获得一种商品的总个数
 public function Getunm($goods_id){
 return $this->item[$goods_id]['num'];
 }

 // 查询购物车中有多少个商品
 public function Getnumber(){
 $num = 0;
 if($this->Gettype() == 0){
 return 0;
 }

 foreach($this->item as $k=>$v){
 $num += $v['num'];
 }
 return $num;
 }

 //计算总价格
 public function Getprice(){
 $price = 0;
 if($this->Gettype() == 0){
 return 0;
 }

 foreach($this->item as $k=>$v){
 $price += $v['num']*$v['num'];
 }
 return $price;
 }

 //清空购物车
 public function Emptyitem(){
 $this->item = array();
 }
 }
?>

<?php
session_start();
header("Content-type = text/html; charset=utf-8");
include_once('Cart.php');
$cart = Cart::Getcat();
$cart->Additem('1','php学习教程(脚本学堂版)','5','9999');

$cart->Additem('1','php学习教程(脚本学堂版)','52','9999');
$cart->Additem('2','php学习教程(脚本学堂版)2','52','99992');
print_r($cart);
var_dump($_SESSION['cat']);
?>