如何在php中添加上一步和下一步按钮？

<?php
session_start();

// 处理表单提交
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $_SESSION['step1_data'] = $_POST['data'];
    header('Location: Step2.php');
    exit;
}
?>

<form method="POST" action="Step1.php">
    <!-- 此处为Step1的表单内容 -->
    <input type="text" name="data" required>
    <input type="submit" value="下一步">
</form>

<?php
session_start();

// 处理表单提交
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $_SESSION['step2_data'] = $_POST['data'];
    header('Location: Step3.php');
    exit;
}
?>

<form method="POST" action="Step2.php">
    <!-- 此处为Step2的表单内容 -->
    <input type="text" name="data" required>
    <input type="submit" value="下一步">
    <input type="button" value="上一步" onclick="history.back()">
</form>

<?php
session_start();

// 处理表单提交
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $_SESSION['step3_data'] = $_POST['data'];
    // 所有步骤完成，进行最终处理
    // ...

    // 清除会话数据
    session_unset();
    session_destroy();
    exit;
}
?>

<form method="POST" action="Step3.php">
    <!-- 此处为Step3的表单内容 -->
    <input type="text" name="data" required>
    <input type="submit" value="完成">
    <input type="button" value="上一步" onclick="history.back()">
</form>