在PHP中重定向到同一页面[但它有不同的内容]

I have a simple 4 page application using PHP sessions. Page 1 asks for username/password, page 2 asks for some information, page 3 displays some results and asks for more info and page 4 is the "success" page. When they are at page 4 I want them to be able to press my submit button and go back to page 2, retaining the username/password from earlier in the session. However, all the pages are named sell-books.php.

I tried using

<?php
    header('Location: '.$_SERVER['PHP_SELF']);
?>

and

$_SESSION['next_page'] =  "point";

The first just gives an error (I have it as the action for a form in an external file)

and the second does not redirect to the page...the page I want to redirect to is a function named request_point()

You need to do something with the session variable, e.g.

if ($_SESSION['next_page'] == "point") {
    request_point();
}