In the early days of PHP e-commerce, a simple script named add-cart.php served as the backbone of countless online stores. The purpose of this script was straightforward: when a user clicked "Add to Cart," the page would send a request containing the product ID ( id ) and, crucially, the product's quantity ( num ) to the server. The server would then place that item into the user's session-based shopping cart. The num parameter therefore is the variable controlling how many of a given product the user intends to purchase. However, due to the primitive security standards of that era, this functionality was frequently implemented with severe vulnerabilities, exposing countless websites to SQL injection, price manipulation, and business logic flaws.
https://vintage-books.com/add-cart.php?num=12
Forces simple casts like (int)$_POST['num'] . Prevents text attacks but doesn't catch negative values. ⚠️ Comprehensive PDO Validation add-cart.php num
The script checks if a $_SESSION['cart'] exists. If not, it initializes one to track items as the user browses.
What "num" typically represents
Return JSON, redirect, or render a message.
$product_id = isset($_POST['product_id']) ? (int)$_POST['product_id'] : 0; $quantity = isset($_POST['num']) ? (int)$_POST['num'] : 1; In the early days of PHP e-commerce, a
if ($product_id <= 0) die("Invalid product ID");
In some systems, an attacker can set the num parameter to a negative value or zero to manipulate the total price. The num parameter therefore is the variable controlling
// basic validation if ($product_id <= 0 || $num <= 0) http_response_code(400); echo json_encode(['error' => 'Invalid input']); exit;
Using simple query parameters like add-cart.php?num= without rigorous backend validation opens up several technical and security issues. 1. Insecure Direct Object References (IDOR)