Javascript 包括一个根据我们的评论用准备好的语句实现查询的示例。Bas：我还包括了你最新的评论解决方案，但是在将来，如果你原来的问题已经得到了回答，那么最好是你开始一个新问题，这样可以使问题及其答案更加集中在易于监督的主题上。 function select_orde

包括一个根据我们的评论用准备好的语句实现查询的示例。Bas：我还包括了你最新的评论解决方案，但是在将来，如果你原来的问题已经得到了回答，那么最好是你开始一个新问题，这样可以使问题及其答案更加集中在易于监督的主题上。

function select_order(order) {
    var item = $(order);
    if (!item.hasClass("selectedRow")) {
        if (!selectedOrderInformation.is(":visible")) {
            switchScreen(selectedOrderInformation, financeOverview);
        }
        item.parent().find(".selectedRow").removeClass("selectedRow");
        item.addClass("selectedRow");
        selectedOrderInformation.html("loading......");
        $.ajax({
            url: "includes/functions/select-order.php",
            type: "get",
            data: {order_id: item.attr("data-order-index")},
            success: function (data) {
                selectedOrderInformation.html(data);
                $("#delete-order-btn").prop("disabled", false);
            }
        });
    } else {
        console.log("DEBUG: Row is already selected");
    }
}

$("#list tbody tr").click(function () {
    select_order(this);
});

if (!empty($_GET['order_id'])) {
    $order_id = $_GET['order_id'];

    $order_data = Database::getInstance()->get_all_data_by_order_id($order_id);
    $order_items = Database::getInstance()->get_order_items_by_order_id($order_id);

    while ($row = mysqli_fetch_array($order_data)) {
        echo "<h1>Klant informatie</h1>";
        echo "<p>Voornaam: " . $row['first_name'] . "</p>";
        echo "<p>Achternaam: " . $row['last_name'] . "</p>";
        echo "<p>Emailadres: " . $row['email_adress'] . "</p>";
        echo "<p>Klant informatie: " . $row['customer_info'] . "</p>";
        echo "<br>";
        echo "<h1>Bestellingsinformatie</h1>";
        echo "<p>Order informatie: " . $row['order_info'] . "</p>";
        echo "<p>Locatie: " . $row['location'] . "</p>";
        echo "<p>Gemaakt op: " . $row['created'] . "</p>";
    }

    echo "<br>";
    echo "<table>";
    echo "<thead>";
    echo "<tr>";
    echo "<th>Product naam</th>";
    echo "<th>Hoeveelheid</th>";

    echo "</tr>";
    echo "</thead>";
    while ($row = mysqli_fetch_array($order_items)) {
        echo "<tr>";
        echo "<td>" . $row['name'] . "</td>";
        echo "<td>" . $row['quantity'] . "</td>";
        echo "</tr>";
    }
    echo "</table>";
    exit;
}

class Database extends mysqli
{

    // single instance of self shared among all instances
    private static $instance = null;

    private $databaseHost = "";
    private $databaseUser = "";
    private $databasePassword = "";
    private $databaseName = "";

    public static function getInstance() {
        if (!self::$instance instanceof self) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    public function __clone() {
        trigger_error('Clone is not allowed.', E_USER_ERROR);
    }

    public function __wakeup() {
        trigger_error('Deserializing is not allowed.', E_USER_ERROR);
    }

    function __construct() {
        parent::__construct($this->databaseHost, $this->databaseUser, $this->databasePassword, $this->databaseName);
        if (mysqli_connect_error()) {
            exit('Connect Error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error());
        }
        parent::set_charset('utf-8');
    }


    function get_all_data_by_order_id($order_id) {
        $query = "SELECT customers.first_name,
                         customers.last_name,
                         customers.email_adress,
                         customers.customer_info,

                         orders.order_info,
                         orders.total_price,
                         orders.location,
                         orders.created

                         FROM customers
                 INNER JOIN orders ON customers.id = orders.customer_id

                 WHERE orders.id = {$order_id}";

        return $this->query($query);
    }

    function get_order_items_by_order_id($order_id) {
        $query = "SELECT `products`.`name`, `orders-items`.`quantity` FROM `orders-items`\n" . "INNER JOIN `products`ON `orders-items`.`products_id` = `products`.`id`\n" . "WHERE order_id=" . $order_id;

        return $this->query($query);
    }
}

if (!empty($_GET['order_id'])) {
    $order_id = $_GET['order_id'];

    $order_data = Database::getInstance()->get_all_data_by_order_id($order_id);
    $order_items = Database::getInstance()->get_order_items_by_order_id($order_id);

    $rows = array();
    while ($row = mysqli_fetch_array($order_data)) {
        $rows[] = $row;
    }
    return json_encode($rows);
    exit;
}

$.ajax({
    url: "includes/functions/select-order.php",
    type: "get",
    data: {order_id: item.attr("data-order-index")},
    success: function (data) {
        selectedOrderInformation.html(data['first_name']);
    }
});

dataType: 'json'

$row = mysqli_fetch_array($order_data);
echo json_encode($row); // instead of $rows

$query = "SELECT p.name, ot.quantity FROM orders-items AS ot
    LEFT JOIN products AS p ON ot.products_id = p.id
    WHERE ot.order_id = " . $order_id;

function get_all_data_by_order_id($order_id) {
    $query = "SELECT c.first_name, c.last_name, c.email_adress, c.customer_info, 
                  o.order_info, o.total_price, o.location, o.created
                  FROM customers AS c
                  LEFT JOIN orders AS o ON c.id = o.customer_id
                  WHERE o.id = :order_id";
    $query_params = array( 
        ':order_id' => $order_id 
    ); 

    $preparedStatement = $this->prepare($query);
    return $preparedStatement->execute($query_params);

}

function get_order_items_by_order_id($order_id) {
    $query = "SELECT p.name, ot.quantity FROM orders-items AS ot
                  LEFT JOIN products AS p ON ot.products_id = p.id
                   WHERE ot.order_id = :order_id;";
    $query_params = array( 
        ':order_id' => $order_id 
    ); 

    $preparedStatement = $this->prepare($query);
    return $preparedStatement->execute($query_params);
}

if (!empty($_GET['order_id'])) {
    $order_id = $_GET['order_id'];

    $order_data = Database::getInstance()->get_all_data_by_order_id($order_id);
    $order_items = Database::getInstance()->get_order_items_by_order_id($order_id);

    $orderObject = array();
    $orderObject['header'] = mysqli_fetch_array($order_data);
    $orderObject['items'] = array();    
    while ($orderedItem = mysqli_fetch_array($order_items)){
        $orderObject['items'][] = $orderedItem;
    }

    echo json_encode($orderObject);
}

....
success: function (data) {
    selectedOrderInformation.html('<h3>' + data['header']['first_name'] + '</h3><ul>');
    $.each(data['items'], function(i, item) {
        selectedOrderInformation.append('<li>' + item['name'] + ' x ' + item['quantity'] + '</li>');
    });
    selectedOrderInformation.append('</ul>');
}
....