我正在學(xué)習(xí)使用 PDO 的教程，我必須使用 MySQLi。在教程中，有這一行：$stmt->execute(array_keys($products_in_cart));我最好的嘗試是這樣做：$stmt->bind_param('i', array_keys($products_in_cart));$stmt->execute();這有效，但僅適用于一種產(chǎn)品，即當(dāng)數(shù)組僅包含一個元素 ([0] => 1) 時。這是整個部分：// Check the session variable for products in cart$products_in_cart = isset($_SESSION['cart']) ? $_SESSION['cart'] : array();$products = array();$subtotal = 0.00;// If there are products in cartif ($products_in_cart) {    // There are products in the cart so we need to select those products from the database    // Products in cart array to question mark string array, we need the SQL statement to include IN (?,?,?,...etc)    $array_to_question_marks = implode(',', array_fill(0, count($products_in_cart), '?'));    $stmt = $mysqli->prepare('SELECT * FROM products WHERE id IN (' . $array_to_question_marks . ')');    // We only need the array keys, not the values, the keys are the id's of the products    $stmt->bind_param('i', array_keys($products_in_cart));    $stmt->execute();    // Fetch the products from the database and return the result as an Array    $products = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);    // Calculate the subtotal    foreach ($products as $product) {        $subtotal += (float) $product['price'] * (int) $products_in_cart[$product['id']];    }}我相信當(dāng)有多個產(chǎn)品時，SQL 語句會因 IN() 子句而變得混亂，即$array_to_question_marks不正確。