<script> // Include the JavaScript code from above </script>
❌ → Allows denial‑of‑stock by adding 9999+ items.
// Validate product if ($product_id <= 0) if ($response_type == 'json') echo json_encode(['success' => false, 'error' => 'Invalid product ID']); exit;
Always use prepared statements with parameterised queries: add-cart.php num
: The chosen volume ( qty or num ) to insert into the user session.
// Expected format: "123:2" $num = $_GET['num'] ?? ''; if (!preg_match('/^(\d+):(\d+)$/', $num, $matches)) die('Invalid format. Use ID:QTY');
$_SESSION['cart'][$product_id] = $new_quantity; <script> // Include the JavaScript code from above
The add-cart.php script and its num parameter are deceptively simple, yet they are the gateway to your entire e‑commerce operation. A small mistake here—a missing validation, a lack of stock check, or a forgotten CSRF token—can open the door to SQL injection, price manipulation, inventory abuse, and other serious security breaches.
) .then(response => response.json()) .then(data => if (data.success) // Update cart badge document.querySelector('.cart-count').textContent = data.cart_count; // Show success message showNotification(data.message, 'success');
When a user clicks "Buy Now," the browser sends a request like this: ://example.com The server then: Receives the ID 123 . ''; if (
He traced the IP. It wasn't coming from a botnet in Eastern Europe or a script kiddie in a basement. The request originated from the internal server—the one sitting three racks over in the climate-controlled silence of the server room.
The user ID returned was 000 . The System Administrator. But Elias was the only admin with clearance for that directory, and he hadn't touched the checkout code in months. Then, a new notification popped up on his screen. POST /checkout/add-cart.php?item_id=USER_ELIAS&num=0