public function testMaxQuantityEnforcement()
if (!$product) die(json_encode(['error' => 'Product not found or unavailable']));
Write a about the first customer's experience with their item. Describe the mysterious items found in Clara's shop.
CREATE TABLE cart_items ( id INT AUTO_INCREMENT PRIMARY KEY, user_id INT NOT NULL, -- 0 for guests (session_id fallback) session_id VARCHAR(128), -- for guests product_id INT NOT NULL, quantity INT NOT NULL CHECK (quantity > 0), added_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP, updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, INDEX (user_id), INDEX (session_id) ); addcartphp num high quality
This single query efficiently handles adding a new item ( INSERT ) or updating the quantity of an existing item ( UPDATE ), reducing database load. PDO Prepared Statements: Eliminates SQL injection risks. 4. Front-End Integration: HTML & AJAX
Correctly handles variations (size, color) as separate cart line items. Security: Prevents SQL injection and session manipulation.
This guide breaks down how to build a production-ready addcart.php script using modern PHP best practices. Architecture of a High-Quality Shopping Cart public function testMaxQuantityEnforcement() if (
PDO::ERRMODE_EXCEPTION, PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC, PDO::ATTR_EMULATE_PREPARES => false, ]); catch (PDOException $e) echo json_encode(['success' => false, 'message' => 'Database connection failed.']); exit; // Validate Request Method if ($_SERVER['REQUEST_METHOD'] !== 'POST') echo json_encode(['success' => false, 'message' => 'Invalid request method.']); exit; // Sanitize and Validate Input Parameters $productId = filter_input(INPUT_POST, 'product_id', FILTER_VALIDATE_INT); $quantity = filter_input(INPUT_POST, 'quantity', FILTER_VALIDATE_INT) ?? 1; if (!$productId || $quantity <= 0) echo json_encode(['success' => false, 'message' => 'Invalid product ID or quantity.']); exit; // Fetch product details and check stock $stmt = $pdo->prepare("SELECT id, name, price, stock FROM products WHERE id = ?"); $stmt->execute([$productId]); $product = $stmt->fetch(); if (!$product) echo json_encode(['success' => false, 'message' => 'Product not found.']); exit; // Calculate total desired quantity in cart $currentCartQty = $_SESSION['cart'][$productId]['quantity'] ?? 0; $totalDesiredQty = $currentCartQty + $quantity; // Inventory Verification if ($totalDesiredQty > $product['stock']) echo json_encode([ 'success' => false, 'message' => "Sorry, only $product['stock'] units are available." ]); exit; // Initialize cart array if empty if (!isset($_SESSION['cart'])) $_SESSION['cart'] = []; // Update Cart Session Structure $_SESSION['cart'][$productId] = [ 'id' => $product['id'], 'name' => $product['name'], 'price' => $product['price'], 'quantity' => $totalDesiredQty ]; // Calculate Total Number ('num') of items in cart $totalCartItemsNum = 0; foreach ($_SESSION['cart'] as $item) $totalCartItemsNum += $item['quantity']; // Store the clean 'num' total in session for global layouts $_SESSION['cart_num'] = $totalCartItemsNum; // Return high-quality JSON response for AJAX manipulation echo json_encode([ 'success' => true, 'message' => 'Product added successfully.', 'cart_num' => $totalCartItemsNum, 'cart_total' => array_sum(array_map(fn($i) => $i['price'] * $i['quantity'], $_SESSION['cart'])) ]); Use code with caution. 4. Frontend Integration: Asynchronous JavaScript (AJAX)
: Enforce strict type declarations ( declare(strict_types=1); ) if this script forms part of a larger object-oriented class system.
// Initialize cart session array if not exists if (!isset($_SESSION['cart'])) $_SESSION['cart'] = []; PDO Prepared Statements: Eliminates SQL injection risks
$requested_num = max(1, min(999, $requested_num)); // clamp between 1 and 999
Generate a unique cryptographic token per session. Validate this token inside add_to_cart.php before altering session states. 2. Optimization and State Preservation
Using a UNIQUE KEY is crucial—it allows us to easily update the quantity if the product is already in the cart rather than inserting a new row. 3. Creating the High-Quality addcart.php Script
A premium addcartphp script never assumes stock. It queries the database live.
Do you need the code for the to display the cart items? What database system are you planning to use?