PHP实现商城购物车类(SESSION+单例模式 )（亲测）

<?php
if(!isset($_SESSION))
    session_start();
//分析购物车
//整站范围内，购物车全局有效
//技术 ： session购物车 + 单例模式
//增删商品,判断商品是否存在
//查询商品种类，数量,查询总金额,返回购物车所有商品
//某商品数量+1  -1
class CartTool{
    private static $ins = null;     //实例保存
    private $items = array();       //保存商品
    //public  $sign = 0;
    //单例
    protected function __construct(){
        //  $this->sign = mt_rand(1,10000);
        
    }
    //防止外界克隆
    final protected function __clone(){
    }
    //单例方法，获取实例
    protected function getIns(){
        if(!(self::$ins instanceof self)){  //若不是自身的实例
            self::$ins = new self();
        }
        return self::$ins;
    }
    //把购物车的单例对象放到session里
    public static function getCart(){
        //session中没有购物车，或者session总的实例不是本身的实例
        if((!(isset($_SESSION['cart'])) || !($_SESSION['cart'] instanceof self))){
            $_SESSION['cart'] = self::getIns();
        }
        return $_SESSION['cart'];
    }
    //添加商品  
    //id: goods_id   goods_name  shop_price  number 
    public function addItem($id,$name,$price,$num = 1){
        if(($this->hasItem($id))){  //若商品已存在，直接加数量
            $this->incNum($id,$num);
            return true;
        }
        $item_temp['id'] = $id;
        $item_temp['name'] = $name;
        $item_temp['price'] = $price;
        $item_temp['num'] = $num;
        $this->items["$id"] = $item_temp;  //二维数组
    }
    //清空购物车
    public function clearItem(){
        $this->items = array();
    }
    
    //判断某商品是否存在
    public function hasItem($id){
        return array_key_exists($id,$this->items);
    }
    //修改购物车中的商品数量  int  goods_id   $num number
    public function modNum($id,$num=1){
        if(!($this->hasItem($id))){
            echo "商品主键不存在,无法修改商品数量";
            return false;
        }
        $this->items[$id]['num'] = $num; 
    }
    //商品数量加一
    public function incNum($id){
        if(!($this->hasItem($id))){
            echo "商品主键不存在，无法增加商品";
            return false;
        }
        $this->items[$id]['num'] += 1; 
    }
    //商品数量减一
    public function decNum($id,$num=1){
        if(!($this->hasItem($id))){
            echo "商品主键不存在，无法减少商品";
            return false;
        }
        
        $this->items[$id]['num'] -= $num;
        //如果减少后商品数量为0了，则把商品从购物车删除 
        if($this->items[$id]['num'] <= 0)
            $this->delItem($id);
    }
    //删除商品 id
    public function delItem($id){
        unset($this->items[$id]);
    }
    //查询购物车中商品种类
    public function getCnt(){
        return count($this->items);
    }
    //查询购物车总商品的个数
    public function getNum(){
        $temp_num = 0;
        if($this->getCnt() == 0)//若购物车没有商品，数量自然为0
            $temp_num = 0;
        foreach($this->items as $item){
            $temp_num += $item['num'];
        }   
        return $temp_num;
    }
    //查询购物车总商品的总金额
    public function getPrice(){
        $temp_money = 0.0;
        if($this->getCnt() == 0)//若购物车没有商品，金额自然为0
            $temp_money = 0.0;
        foreach($this->items as $item){
            $temp_money += ($item['num'] * $item['price']);
        }   
        return $temp_money;
    }
    //返回购物车所有商品，空：返回商品数组  任意字符串：数组形式返回所有商品的名字
    public function getAllGoods($fun=''){
        if($fun == '')
            return $this->items;
        //返回所有商品的名字
        $temp_arr = array();
        foreach($this->items as $k=>$v){
            $temp_arr[] = array( $k=>$v['name'] );
        }
        return $temp_arr;
    }
}
/** php 测试 代码
$cart = CartTool::getCart();
if(isset($_GET['test']) && $_GET['test'] == 'add'){
    $cart->addItem('1',"雪",'88888');
    $cart->addItem('5',"雪1",'88888');
    $cart->addItem('8',"雪2",'88888');
    echo 'add ok';
}else if(isset($_GET['test']) &&  $_GET['test'] == 'clear'){
    $cart->clearItem();
    echo "successufl ok";
}else if(isset($_GET['test']) &&  $_GET['test'] == 'num'){
    $cart->modNum(8,3);
    echo "modify ok";
}else if(isset($_GET['test']) &&  $_GET['test'] == 'add1'){
    $cart->incNum(8);
    echo "modify ok";
}else if(isset($_GET['test']) &&  $_GET['test'] == 'dec1'){
    $cart->decNum(8);
    echo "modify ok";
}else if(isset($_GET['test']) &&  $_GET['test'] == 'price'){
    echo "总共",$cart->getNum(),"种商品";
    $pri = $cart->getPrice();
    echo "总共",$pri,'元';
}else if(isset($_GET['test']) &&  $_GET['test'] == 'all'){
    
    print_r( $cart->getAllGoods());
    echo "<hr/>";
    print_r( $cart->getAllGoods(1));
}else{
    print_r($cart);
}
echo "<br/>";
//print_r(CartTool::getCart());
 */
?>