Php Id 1 Shopping

$total = 0; while ($row = mysqli_fetch_assoc($result)) $product_id = $row['product_id']; $quantity = $row['quantity'];

When a user wants to view a product, the PHP script retrieves the ID from the URL: php id 1 shopping

: Ensure the "ID" is always a number and never a string of code. $total = 0

At first glance, this works perfectly. The user clicks "View Item," and the page loads. But what happens if the user changes the URL from id=1 to id=2 ? $quantity = $row['quantity']