// Re-check stock against new total if ($new_quantity > $product['stock_quantity']) die(json_encode(['error' => 'Cannot add. Total would exceed stock.']));
<input type="number" id="quantity" name="num" min="1" max="99" step="1" value="1"> <button id="add-to-cart">Add to Cart</button> <script> document.getElementById('add-to-cart').addEventListener('click', async () => ); </script> Unit Test Example (PHPUnit) public function testAddToCartWithValidNum() addcartphp num high quality
// Initialize cart session array if not exists if (!isset($_SESSION['cart'])) $_SESSION['cart'] = []; // Re-check stock against new total if ($new_quantity