//修改便當數量


    include_once('Bag.inc');
    session_start();
    
    $lunchbox_number = array_keys($_POST);
    for($i=0;$i< count($lunchbox_number);$i++){
        $_SESSION['bag']->set_order_quantity($lunchbox_number[$i],$_POST[$lunchbox_number[$i]]);	
    }
    header("Location:bag_content.php");   

//set_order_quantity()

 function set_order_quantity($item_number,$quantity){
        $this->quantity[$item_number] = $quantity;
        $this->price[$item_number] = $quantity * $this->single_cost[$item_number];
        $this->total_cost = array_sum($this->price);
    }