product action of food order in php

 <?php

if(!empty($_GET["action"])) 

{

$productId = isset($_GET['id']) ? htmlspecialchars($_GET['id']) : '';

$quantity = isset($_POST['quantity']) ? htmlspecialchars($_POST['quantity']) : '';

switch($_GET["action"])

 {

    case "add":

        if(!empty($quantity)) {

                                $stmt = $db->prepare("SELECT * FROM dishes where D_ID= ?");

                                $stmt->bind_param('i',$productId);

                                $stmt->execute();

                                $productDetails = $stmt->get_result()->fetch_object();

                                $itemArray = array($productDetails->D_ID=>array('FName'=>$productDetails->FName, 'D_ID'=>$productDetails->D_ID, 'quantity'=>$quantity, 'price'=>$productDetails->price));

                    if(!empty($_SESSION["cart_item"])) 

                    {

                        if(in_array($productDetails->D_ID,array_keys($_SESSION["cart_item"]))) 

                        {

                            foreach($_SESSION["cart_item"] as $k => $v) 

                            {

                                if($productDetails->D_ID == $k) 

                                {

                                    if(empty($_SESSION["cart_item"][$k]["quantity"])) 

                                    {

                                    $_SESSION["cart_item"][$k]["quantity"] = 0;

                                    }

                                    $_SESSION["cart_item"][$k]["quantity"] += $quantity;

                                }

                            }

                        }

                        else 

                        {

                                $_SESSION["cart_item"] = $_SESSION["cart_item"] + $itemArray;

                        }

                    } 

                    else 

                    {

                        $_SESSION["cart_item"] = $itemArray;

                    }

            }

            break;

            

    case "remove":

        if(!empty($_SESSION["cart_item"]))

            {

                foreach($_SESSION["cart_item"] as $k => $v) 

                {

                    if($productId == $v['D_ID'])

                        unset($_SESSION["cart_item"][$k]);

                }

            }

            break;

            

    case "empty":

            unset($_SESSION["cart_item"]);

            break;

            

    case "check":

            header("location:checkout.php");

            break;

    }

}