Many inexperienced developers concatenate the num parameter directly into an SQL query to check stock levels before adding to cart.
To build a reliable cart, our PHP script needs to answer three questions every time a user clicks "Add to Cart": Is there already a cart session? If not, we need to create one. Is this product already in the cart? If yes, we need to the new quantity to the existing quantity. Is this a brand new product? If yes, we add it as a new line item. Step-by-Step Implementation: add-cart.php Create a file named add-cart.php add-cart.php num
Elias squinted. The num parameter was supposed to represent the quantity of items a user added to their basket. The frontend had validation to prevent negative numbers. The backend had a sanitization script. Yet, there it was: a request for antique brass clocks. Is this product already in the cart
$quantity = max(1, min(999, $quantity)); If yes, we add it as a new line item
Security and validation considerations
?>
<script> // Include the JavaScript code from above </script>