简单的html/php表单在同一页面上输出

<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="POST">
    <!-- 表单元素 -->
    <input type="text" name="name" placeholder="姓名">
    <input type="email" name="email" placeholder="邮箱">
    <input type="submit" value="提交">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];

    // 在页面上输出表单数据
    echo "姓名: " . $name . "<br>";
    echo "邮箱: " . $email . "<br>";
}
?>