如何将PDO的execute（$ variable）转换为MySQLi语句

Question

我正在学习使用PDO的教程，我必须使用MySQLi。在本教程中，有以下一行：

$stmt->execute(array_keys($products_in_cart));

并且我最好的尝试是这样做：

$stmt->bind_param('i', array_keys($products_in_cart));
$stmt->execute();

这有效，但仅适用于一种乘积，即，当数组仅包含一个元素（[0] => 1）时。

这里是整个部分：

// 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 cart
if ($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']];
    }
}

我相信当有几种产品时，即IN（）子句会弄乱SQL语句，即$array_to_question_marks不合适。

Answer 1

MySQLi比PDO困难。我强烈建议尽可能使用PDO。

如果要在mysqli中绑定未知数量的参数，则需要创建带有类型的字符串，然后对数组进行splat处理。

$arrayKeys = array_keys($products_in_cart);
$stmt->bind_param(str_repeat("s", count($arrayKeys)), ...$arrayKeys);
$stmt->execute();

Answer 2

PDO和MySQLi不会在准备好的语句上共享行为。您应该阅读特定的MySQLi教程以实现您想要做的事情...

mySQL bind_param with IN(?)