might subtract from the total price, potentially resulting in a negative checkout balance or "free" items. Integer Overflow : Submitting extremely large numbers (e.g., 9999999999999
When a user clicks "Buy Now," the browser sends a request like this: ://example.com The server then: Receives the ID 123 . add-cart.php num
$productId = filter_input(INPUT_POST, 'product_id', FILTER_VALIDATE_INT); $quantity = filter_input(INPUT_POST, 'quantity', FILTER_VALIDATE_INT); might subtract from the total price, potentially resulting