How can I redirect in PHP without header errors?

Question

How can I redirect in PHP with this setup below without getting header output errors, I understand that nothing can be printed to the browser before a header is set, I am lookin

Answer 1

Can't you just do this:

<?php
validlogin($url); // call the function here
include ('header.inc.php');
include ('SOME-FILE-HERE.php');
include ('footer.inc.php');
?>

Or, put the include files in every one of the "SOME-FILE-HERE"-type files, if that's possible, so you end up with:

<?php
validlogin($url); // call the function here
include ('header.inc.php');
?>

<h1>Page heading</h1>
...page content etc...

<?php
include ('footer.inc.php');
?>