ช่วยหน่อยเรื่องการสร้าง cart ตะกร้าสินค้า ใน java ค่ะ

$productId = $_REQUEST["productId"];
$product = readProductById($productId);
if(!isset($_SESSION["cart"]))
	{
		$_SESSION["cart"] = array();
		$cart = $_SESSION["cart"];
		$cart["productList"] = array();
		$productList =  $cart["productList"];
		$productList["$productId"]=1;
		
		$cart["total"]=1;
		$cart["totalPrice"]=$product["pro_price_unit"];
		
		$cart["productList"]=$productList;
		$_SESSION["cart"]=$cart;
		
	}else{
		$cart = $_SESSION["cart"];
		$productList = $cart["productList"];
		
		if(isset($productList["$productId"]))
		{
			$productList["$productId"]=$productList["$productId"]+1;
			
		}else{
			$productList["$productId"]=1;
		}
		
		$cart["total"]=$cart["total"]+1;
		$cart["totalPrice"]=$cart["totalPrice"]+$product["pro_price_unit"];
		
		$cart["productList"]=$productList;
		$_SESSION["cart"]=$cart;
		
	}