Num New! — Add-cart.php

if (isset($_SESSION['cart'][$product_id])) $new_qty = $_SESSION['cart'][$product_id] + $quantity; // Re-validate sum if ($new_qty > 99) $new_qty = 99;

This code is a disaster waiting to happen. It trusts user input implicitly, has no CSRF protection, no inventory check, and no ownership validation. add-cart.php num

Conclusion A parameter named num on add-cart.php most commonly denotes quantity. Implementing safe, user-friendly cart behavior requires strict validation, server-side authoritative checks for product and pricing, CSRF protections, and clear UX for edge cases like stock limits. The concise PHP example demonstrates basic secure handling: sanitize inputs, check DB for product and stock, update session cart, and return a structured response. Decimal Injection

// Vulnerable code $id = $_GET['num']; $result = mysqli_query($conn, "SELECT * FROM products WHERE id = $id"); user-friendly cart behavior requires strict validation

if (!isset($_SESSION['cart'])) $_SESSION['cart'] = [];

) can crash the calculation logic or cause the price to wrap around to zero. Decimal Injection