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)
class CartTest extends TestCase
If the input is passed directly into a raw SQL query further down the line without sanitization, it can easily lead to SQL Injection (SQLi).
While client-side guardrails like min="1" improve user experience by steering legitimate users away from mistakes, . An attacker can bypass HTML constraints in seconds using browser developer tools or tools like Postman. The PHP backend must always remain the ultimate authority. Conclusion
A premium e-commerce script balances performance with data integrity. To achieve this, your PHP cart should utilize a hybrid approach: for immediate, low-latency user interactions and a relational database (MySQL/PostgreSQL) for persistent storage. Why Sessions for Active Carts? addcartphp num high quality
50 megabytes of output memory. For one client.
First, ensure you have a database table for your products. Here is a simple example:
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Four seconds? For an atomic operation? She scrolled up. An attacker can bypass HTML constraints in seconds
| Storage Method | Best For | Pros | Cons | |---|---|---|---| | Session | Guests, small stores | Fast, simple, no DB required | Not persistent across devices | | Database | Logged-in users, cross-device sync | Persistent, queryable, scalable | Slower, requires DB setup | | Redis | High-traffic sites, real-time | Extremely fast, atomic operations | Additional infrastructure |
function addToCart(productId, quantity) const formData = new FormData(); formData.append('product_id', productId); formData.append('num', quantity); fetch('add-cart.php', method: 'POST', body: formData ) .then(response => response.json()) .then(data => if(data.success) document.getElementById('cart-badge').innerText = data.cart_count; alert(data.message); else alert('Error: ' + data.message); ) .catch(error => console.error('Error:', error)); Use code with caution. Security Checklist for Production Deployment
// Always assume input is a string $rawQty = $_POST['quantity'] ?? '';
// Create unique cart item key (especially important for variants) $cartKey = $productId; if (!empty($variants)) $cartKey .= '_' . md5(json_encode($variants)); Below is a robust
Below is a robust, object-ready procedural script designed to handle cart additions securely, with specific guards built in for exceptionally high numerical inputs.
public function __construct($pdo) $this->pdo = $pdo; if (!isset($_SESSION['cart'])) $_SESSION['cart'] = [];
When scaling, use database transactions ( SELECT ... FOR UPDATE ) to prevent multiple users from checking out the final item in stock simultaneously.
“High quality isn't just about clean syntax. It's about anticipating the degenerate case at 3:00 AM.”
Modern e‑commerce sites use AJAX to add items without reloading the page. Your PHP backend remains unchanged – it simply returns JSON instead of a redirect.