Go Back to Previous Page

Try this:

$previous = "javascript:history.go(-1)";
if(isset($_SERVER['HTTP_REFERER'])) {
    $previous = $_SERVER['HTTP_REFERER'];
}

in html:

<a href="<?= $previous ?>">Back</a>

The JavaScript code is initialize as fallback for HTTP_REFERER variable sometimes not work.

You can use a link to invoke history.go(-1) in Javascript, which is essentially equivalent to clicking the Back button. Ideally, however, it'd be better to just create a link back to the URL from whence the user was posted to the form - that way the proper "flow" of history is preserved and the user doesn't wonder why they have something to click "Forward" to which is actually just submitting the form again.