php回显用户结果相同的页面错误与动作标签不允许PHP内部

-------------------UPDATE SOLVED the file was a .html extension and not a .php file - - Thanks for the help!

I've seen a few posts explaining how to echo html submitted form information on the same page using php. When I try to implement this I always get an error when playing php tags inside the form action = "".

Here is the code...

Hello <?php echo $_POST["name"]; ?><br>

    <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
        Name: <input type="text" name="name">
        <input type="submit">
    </form>

Just a try:

Hello <?php echo $_POST["name"]; ?><br>
<form action=<?php echo '"' . $_SERVER['PHP_SELF'] . '"'; ?> method="post">
    Name: <input type="text" name="name">
    <input type="submit">
</form>

Try this:

<?php echo isset($_POST["name"])?"Hello, " . $_POST["name"]:""; ?><br>

<form action=<?php echo '"' . $_SERVER['PHP_SELF'] . '"'; ?> method="post">
    Name: <input type="text" name="name">
    <input type="submit">
</form>