Implementation code of php shopping cart class (single case mode)

/**
 * php shopping cart class
 * Singleton mode
 * Edit bbs.it-home.org
*/
 class Cart{
 static protected $ins; //Instance variable
 protected $item = array(); //Place items Container
 //External calls are prohibited
 final protected function __construct(){
 }
 //Cloning is prohibited
 final protected function __clone(){
 }
 //Internal instantiation of the class
 static protected function Getins(){
 if(!(self::$ins instanceof self)){
 self::$ins = new self() ;
 }
 return self::$ins;
 }
 //In order to save the product across pages, put the object into the session
 public function Getcat(){
 if(!($_SESSION['cat']) || !($_SESSION['cat'] instanceof self)){
 $_SESSION['cat'] = self::Getins();
 }
 return $_SESSION['cat'];
 }
 //Check when enqueueing, whether it exists in $item.
 public function Initem($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']; //Return the number of this product
 }
 }
 //Add one Goods
 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(); //A product is an array
 $this-> ;item[$goods_id]['num'] = $num; //Purchase quantity of this product
 $this->item[$goods_id]['name'] = $name; //Product name
 $this ->item[$goods_id]['price'] = $price; //unit price of the item
 }
 //reduce one item
 public function Reduceitem($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'] -=$num;
 }
 }
 //Remove one Goods
 public function Delitem($goods_id){
 if($this->Initem($goods_id)){
 unset($this->item[$goods_id]);
 }
 }
  //Return to the list of purchased items
 public function Itemlist(){
 return $this->item;
 }
 //How many types of items are there in total?
 public function Gettype( ){
 return count($this->item);
 }
 //Get the total number of a product
 public function Getunm($goods_id){
 return $this- >item[$goods_id]['num'];
 }
 // Check how many items are in the shopping cart
 public function Getnumber(){
 $num = 0;
 if ($this->Gettype() == 0){
 return 0;
 }
 foreach($this->item as $k=>$v){
 $ num += $v['num'];
 }
 return $num;
 }
 //Calculate the total price
 public function Getprice(){
 $price = 0;
 if ($this->Gettype() == 0){
 return 0;
 }
 foreach($this->item as $k=>$v){
 $ price += $v['num']*$v['num'];
 }
 return $price;
 }
 //Clear the shopping cart
 public function Emptyitem(){
 $this->item = array();
 }
 }
?>

Call example:

include_once('Cart.php');
$cart = Cart::Getcat();
$cart->Additem('1','php learning tutorial (programmer Home Edition)','5','9999');
print_r($cart);
?>