如何使用php prepared-statement从MySQL返回Json格式的对象数组

$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名";

// 使用mysqli扩展连接到MySQL数据库
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 使用PDO扩展连接到MySQL数据库
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
    die("连接失败: " . $e->getMessage());
}

$stmt = $conn->prepare("SELECT column1, column2 FROM table WHERE condition = ?");
$stmt->bind_param("s", $condition);
$stmt->execute();
$result = $stmt->get_result();

$data = array();
while ($row = $result->fetch_assoc()) {
    $data[] = $row;
}

$json = json_encode($data);

header('Content-Type: application/json');
echo $json;

$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名";

// 使用mysqli扩展连接到MySQL数据库
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 使用PDO扩展连接到MySQL数据库
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
    die("连接失败: " . $e->getMessage());
}

$stmt = $conn->prepare("SELECT column1, column2 FROM table WHERE condition = ?");
$stmt->bind_param("s", $condition);
$stmt->execute();
$result = $stmt->get_result();

$data = array();
while ($row = $result->fetch_assoc()) {
    $data[] = $row;
}

$json = json_encode($data);

header('Content-Type: application/json');
echo $json;