PHP undefined array for website shopping cart

Question

i have found out that when i press the update button, regardless of doing anything, it comes up with this message:

Warning: Undefined array key "Product_Name" in C:\xampp\htdocs\website\bootsp.php on line 35
Warning: Undefined array key "product_qty" in C:\xampp\htdocs\website\bootsp.php on line 36
Warning: Undefined array key "Price" in C:\xampp\htdocs\website\bootsp.php on line 37
Warning: Undefined array key "Product_ID" in C:\xampp\htdocs\website\bootsp.php on line 38 array(1) { [1]=> string(1) "1" }

what i suspect is happening, is that when i press the update button regardless of pressing the remove checklist is that it automatically adds a null variable to the $ variables which messes up my code, i am not sure why this happens.

boots page php code for the shopping list:

<?php
if(isset($_SESSION["cart_products"]) && count($_SESSION["cart_products"])>0)
{
    
    echo '<h3>Your Shopping Cart</h3>';
    echo '<form method="post" action="cart_update.php">';
    echo '<table width="100%"  cellpadding="6" cellspacing="0">';
    echo '<thead><tr><th>Quantity</th><th>Name</th><th>Remove</th></tr></thead>';
    echo '<tbody>';


    $total =0;
    $b = 0;

    foreach ($_SESSION["cart_products"] as $cart_itm)
    {
        $Product_Name = $cart_itm["Product_Name"];
        $product_qty = $cart_itm["product_qty"];
        $Price = $cart_itm["Price"];
        $Product_ID = $cart_itm["Product_ID"];
        
        $bg_color = ($b++%2==1) ? 'odd' : 'even'; //zebra stripe

        echo '<tr class="'.$bg_color.'">';
        echo '<td><input type="text" size="2" maxlength="2" name="product_qty['.$Product_ID.']" value="'.$product_qty.'" /></td>';
        echo '<td>'.$Product_Name.'</td>';
        echo '<td><input type="checkbox" name="remove_code[]" value="'.$Product_ID.'" /> Remove</td>';
        echo '</tr>';
        $subtotal = ($Price * $product_qty);
        $total = ($total + $subtotal);
        var_dump($cart_itm);
        //unset($_SESSION["cart_products"]);
    }

    echo '<tr><td>&nbsp;</td></tr>';
    echo '<tr>';
    
    echo '<td>&nbsp;</td>';
    echo '<td>';
    echo '<button type="submit" id="myButton">Update</button></td>';


    echo '<td><a href="view_cart.php" id="myButton" style="width: 18%; padding-left: 8px;">Checkout</a>';
    echo '</td>';
    echo '</tr>';
    echo '</tbody>';
    echo '</table>';
    
    $current_url = urlencode($url="http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']);
    echo '<input type="hidden" name="return_url" value="'.$current_url.'" />';
    echo '</form>';
}
?>

my cart update php file code:

<?php
include 'config.php';
session_start();
if(isset($_POST["type"]) && $_POST["type"]=='add'){
    foreach($_POST as $key => $value){ //add all post vars to new_product array
        $new_product[$key] = filter_var($value, FILTER_SANITIZE_STRING);
    }
    //remove unecessary vars
    unset($new_product['type']);
    unset($new_product['return_url']);
    //$temp_prod_id = $new_product['Product_ID'];
    $results = "select Product_ID, Product_Name, Product_Img_name, Category, Price, Description FROM products where Product_ID = '".$new_product['Product_ID']."'";
    $results2 = mysqli_query($con,$results);
    if ($results2>null){
        while ($obj = mysqli_fetch_row($results2)) {
            //$Product_ID = $new_product['Product_ID'];
            $new_product['Product_ID']=$obj[0];
            $new_product['Product_Name']=$obj[1];
            $new_product['Product_Img_name']=$obj[2];
            $new_product['Price']=$obj[4];

            if(isset($_SESSION["cart_products"])){  //if session var already exist
                if(isset($_SESSION["cart_products"][$new_product['Product_ID']])) //check item exist in products array
                {
                    unset($_SESSION["cart_products"][$new_product['Product_ID']]); //unset old array item
                }           
            }
            $_SESSION["cart_products"][$new_product['Product_ID']] = $new_product; //update or create product session with new item
        }
    }
}


if(isset($_POST["product_qty"]) || isset($_POST["remove_code"])){
    //update item quantity in product session
    if(isset($_POST["product_qty"]) && is_array($_POST["product_qty"])){
        foreach($_POST["product_qty"] as $key => $value){
            if(is_numeric($value)){
                $_SESSION["cart_products"]["product_qty"][$key] = $value;
            }
        }
    }
    //remove an item from product session
    if(isset($_POST["remove_code"]) && is_array($_POST["remove_code"])){
        foreach($_POST["remove_code"] as $key){
            unset($_SESSION["cart_products"][$key]);
        }   
    }
}

$return_url = (isset($_POST["return_url"]))?urldecode($_POST["return_url"]):''; //return url
header('Location:'.$return_url);
?>