A high-quality add-to-cart system requires a dynamic UI. Here is the HTML/JS that interacts with the above PHP script. 4.1 HTML Structure (Product Page) <div class="product" data-product-id="42"> <h3>Premium Widget</h3> <p>Price: $29.99</p> <div class="quantity-control"> <button class="qty-decrement" aria-label="Decrease quantity">-</button> <input type="number" id="qty-num" name="num" value="1" min="1" max="50" step="1"> <button class="qty-increment" aria-label="Increase quantity">+</button> </div> <button class="add-to-cart-btn" data-id="42">Add to Cart</button> <div class="cart-feedback"></div> </div> 4.2 JavaScript (High-Quality Event Handling) // high-quality-cart.js document.querySelectorAll('.add-to-cart-btn').forEach(btn => btn.addEventListener('click', async function(e) quantity < 1) quantity = 1; if (quantity > maxStock) quantity = maxStock; const formData = new URLSearchParams(); formData.append('id', productId); formData.append('num', quantity); formData.append('csrf_token', getCsrfToken()); // fetch from meta tag try const response = await fetch('/addcart.php', method: 'POST', headers: 'Content-Type': 'application/x-www-form-urlencoded', 'X-Requested-With': 'XMLHttpRequest' , body: formData ); const result = await response.json(); const feedbackDiv = this.closest('.product').querySelector('.cart-feedback'); if (result.success) feedbackDiv.innerHTML = `<span class="success">✓ $result.message (Total: $result.cart_count)</span>`; updateCartIcon(result.cart_count); // Optional: animate the cart icon else feedbackDiv.innerHTML = `<span class="error">❌ $result.error</span>`; setTimeout(() => feedbackDiv.innerHTML = '', 3000); catch (err) console.error('Cart error:', err); );
if (!empty($_SESSION['cart'])) $ids = array_keys($_SESSION['cart']); $placeholders = implode(',', array_fill(0, count($ids), '?')); $stmt = $pdo->prepare("SELECT id, name, price, stock_quantity FROM products WHERE id IN ($placeholders)"); $stmt->execute($ids); $products = $stmt->fetchAll(PDO::FETCH_ASSOC); addcartphp num high quality
);
// Get and sanitize inputs $product_id = filter_input(INPUT_POST, 'id', FILTER_VALIDATE_INT); $requested_num = filter_input(INPUT_POST, 'num', FILTER_VALIDATE_INT); A high-quality add-to-cart system requires a dynamic UI
// --- OPTIONAL: Sync with database for logged-in users --- if (isset($_SESSION['user_id'])) $upsert = $pdo->prepare(" INSERT INTO user_carts (user_id, product_id, quantity) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE quantity = ? "); $upsert->execute([$_SESSION['user_id'], $product_id, $cart[$product_id]['quantity'], $cart[$product_id]['quantity']]); div class="product" data-product-id="42">