PHP 재고 관리 시스템의 주문 관리 기능을 위한 코드 생성

CREATE TABLE orders (
    id INT(11) AUTO_INCREMENT PRIMARY KEY,
    customer_name VARCHAR(255) NOT NULL,
    order_date DATETIME NOT NULL,
    total_amount DECIMAL(10, 2) NOT NULL
);

function insertOrder($customer_name, $order_date, $total_amount) {
    $conn = new mysqli("localhost", "username", "password", "dbname");
    
    if ($conn->connect_error) {
        die("连接数据库失败：" . $conn->connect_error);
    }
    
    $sql = "INSERT INTO orders (customer_name, order_date, total_amount) VALUES ('$customer_name', '$order_date', $total_amount)";
    
    if ($conn->query($sql) === TRUE) {
        echo "订单已成功插入.";
    } else {
        echo "插入订单失败: " . $conn->error;
    }
    
    $conn->close();
}

function getOrders() {
    $conn = new mysqli("localhost", "username", "password", "dbname");
    
    if ($conn->connect_error) {
        die("连接数据库失败：" . $conn->connect_error);
    }
    
    $sql = "SELECT * FROM orders";
    
    $result = $conn->query($sql);
    
    if ($result->num_rows > 0) {
        while ($row = $result->fetch_assoc()) {
            echo "订单ID: " . $row["id"]. " - 客户姓名: " . $row["customer_name"]. " - 订单日期: " . $row["order_date"]. " - 总金额: " . $row["total_amount"]. "<br>";
        }
    } else {
        echo "没有订单记录.";
    }
    
    $conn->close();
}

function updateOrder($order_id, $total_amount) {
    $conn = new mysqli("localhost", "username", "password", "dbname");
    
    if ($conn->connect_error) {
        die("连接数据库失败：" . $conn->connect_error);
    }
    
    $sql = "UPDATE orders SET total_amount = $total_amount WHERE id = $order_id";
    
    if ($conn->query($sql) === TRUE) {
        echo "订单已成功更新.";
    } else {
        echo "更新订单失败: " . $conn->error;
    }
    
    $conn->close();
}

function deleteOrder($order_id) {
    $conn = new mysqli("localhost", "username", "password", "dbname");
    
    if ($conn->connect_error) {
        die("连接数据库失败：" . $conn->connect_error);
    }
    
    $sql = "DELETE FROM orders WHERE id = $order_id";
    
    if ($conn->query($sql) === TRUE) {
        echo "订单已成功删除.";
    } else {
        echo "删除订单失败: " . $conn->error;
    }
    
    $conn->close();
}