PHP 関数を使用してフォーム データの保存と表示を行うにはどうすればよいですか?

<?php
// 数据库连接配置
$host = "localhost";
$username = "root";
$password = "";
$database = "mydb";

// 连接数据库
$conn = mysqli_connect($host, $username, $password, $database);

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

// 获取表单数据
$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];

// 构建SQL语句
$sql = "INSERT INTO form_data (name, email, message) VALUES ('$name', '$email', '$message')";

// 执行SQL语句
if (mysqli_query($conn, $sql)) {
    echo "数据存储成功";
} else {
    echo "数据存储失败: " . mysqli_error($conn);
}

// 关闭数据库连接
mysqli_close($conn);
?>

<?php
// 数据库连接配置
$host = "localhost";
$username = "root";
$password = "";
$database = "mydb";

// 连接数据库
$conn = mysqli_connect($host, $username, $password, $database);

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

// 查询数据库并获取数据
$sql = "SELECT * FROM form_data";
$result = mysqli_query($conn, $sql);

// 显示数据
if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        echo "姓名: " . $row['name'] . "<br>";
        echo "邮箱: " . $row['email'] . "<br>";
        echo "留言: " . $row['message'] . "<br><br>";
    }
} else {
    echo "没有数据";
}

// 关闭数据库连接
mysqli_close($conn);
?>