Introduction Online shopping carts are a core component of e-commerce applications. One common pattern is using a server-side script (for example, add-cart.php) that accepts parameters to add items to a user's cart. This essay examines the typical role of an add-cart.php script, the meaning and use of a parameter often labeled "num" (or similar), security and validation considerations, and a simple implementation example in PHP. It also discusses edge cases and best practices for maintainability and user experience.
While num usually refers to quantity, sometimes vulnerabilities in add-cart.php allow the user to modify the price parameter alongside the quantity. add-cart.php num
This article explores how to build a secure and efficient add-cart.php script from scratch. Essay: Understanding and Implementing add-cart
Insecure Direct Object Reference (IDOR): Allowing users to access or edit cart items belonging to other sessions. Server Logic: The server processes the cart update
if ($_SERVER['REQUEST_METHOD'] !== 'POST') http_response_code(405); die("Method not allowed");
This vulnerability arises when an application relies on Client-Side Trust. The server assumes that the data sent by the browser—specifically the num (number/quantity) parameter—is valid and has not been tampered with.
add-cart.php?num=X?In poorly architected legacy systems or beginner PHP projects, add-cart.php acts as a direct gateway to the cart session. The num parameter typically represents one of two things: