Mysql结果，数组到json，但添加了一个元素

<?php
// 连接到MySQL数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 执行查询语句
$sql = "SELECT * FROM your_table";
$result = $conn->query($sql);

// 将查询结果保存在数组中
$data = array();
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        $data[] = $row;
    }
}

// 添加元素
$newElement = array("key" => "value");
$data[] = $newElement;

// 转换为JSON
$jsonData = json_encode($data);

// 输出JSON结果
echo $jsonData;

// 关闭数据库连接
$conn->close();
?>