不从购物车中移除物品

以下是我的php代码，显示了如何从购物车中删除物品。网页上没有显示错误，但项目没有删除，购物车没有更新。用完整的代码编辑

    <div class="product_box">
            <form action="cart.php" method="post" enctype="multipart/data">

            <table align="center" width="700" bgcolor="skyblue">

                <tr>
                    <th>Remove</th>
                    <th>Product (s) </th>
                    <th>Quantity</th>
                    <th>Total Price</th>
                </tr>

        <?php  



        $total = 0;

         global $db;

         $ip = getIp();

         $sel_price ="select * from cart where ip_add='$ip'";

         $run_price = mysqli_query($db, $sel_price);

         while ($p_price=mysqli_fetch_array($run_price)) {

            $pro_id = $p_price['p_id'];

            $pro_price = "select * from products where product_id='$pro_id'";

            $run_pro_price = mysqli_query($db, $pro_price);

            while ($pp_price = mysqli_fetch_array($run_pro_price)) {

                $product_price = array($pp_price ['product_price']);

                $product_title = $pp_price['product_title'];

                $product_image = $pp_price['product_img1'];

                $single_price = $pp_price['product_price'];




                $values = array_sum($product_price);
                $total +=$values;

          //echo "Rs ." . $total;





            ?>

            <tr align="center">
                <td><input type="checkbox" name="remove[]"></td>
                <td><?php echo $product_title; ?><br>
                    <img src="admin_area/product_images/<?php echo $product_image;?>" width="50px" height="50px">
                 </td>
                <td><input type="text" name="qty" size="3"></td>
                <td><?php echo "Rs." . $single_price ?></td>
            </tr>



            <?php   } } ?> 
            <tr align="right">
                <td colspan="3">
                    <b> Sub Total: </b>
                </td>
                <td>
                    <?php echo "Rs." .$total; ?>
                </td>
            </tr>
            <tr align="center">
                <td colspan="1"><input type="submit" name="update_cart" value="Update Cart"></td>
                <td><input type="submit" name="continue" value="Continue Shopping"></td>
                <td><button><a href="checkout.php">Checkout</a></button></td>
            </tr>


            </table>

            </form>

            <?php
$ip = getIp();

        if (isset($_POST['update_cart'])) {

            foreach ($_POST['remove'] as $remove_id) {

                $delete_product = "delete from cart where p_id=".$remove_id." AND ip_add=".$ip;
                $run_delete = mysqli_query($db, $delete_product);
                if ($run_delete) {
                    echo "<script>window.open('cart.php','_self')</script>";
                }

            }
        }

}


             ?>
        </div>
        </div>

我试图通过在if语句后放置以下代码来检查错误，但是没有用。

else { echo mysqli_error($db);}

请帮忙谢谢。