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 looking for a solution, not an explanation of why it happens please.

<?PHP
// include header
include ('header.inc.php');



// In my body section file if this is a page that requires a user be logged in then
// I run a function validlogin($url-of-page-we-are-on); inside of that file
//the function is below, it outputs a redirect to login page if not logged in

// include body of page we want
include ('SOME-FILE-HERE.php');



// include footer
include ('footer.inc.php');



// here is the function that is in the body pages, it is only called on a page that we require a logged in user so there are hundreds of pages that do have this and a bunch that don't, it's on a page to page basis
function validlogin($url) {
    if ($_SESSION['auto_id'] == '') {
     $msg = 'Please login';
     $_SESSION['sess_login_msg'] = $msg;
     $_SESSION['backurl'] = $url;
     $temp = '';
     header("Location: /");
     exit();
    }
}
?>

I would like to user php's header function and not a meta or javascript redirect

Also maintainning a list of pages that require login or not is not an option here if possible

Answer 1

Use ob_start() in the first line even befor the include. so you can set headers anytime.

Answer 2

As long as you have no script output before the header() function you should be fine. Check there are no echo's or whitespace. Also putting ob_start() at the beginning can help. sometimes there is invisible whitespace - changing the format of your document to ANSI or Unicode may help!

As a note (although I think you already know) header does not terminate the script so the exit() (which you have) is a definite requirement.

Answer 3

Does the footer.inc.php and SOME-FILE-HERE.php write to the response stream immediately? Because if so, this won't work as you will have already written something before you sent the headers.

Answer 4

You need to buffer the ouput so that the HTTP header is not send on the first output. You can either buffer any ouput implicitly by enabling ouput_buffering or explicitly by calling ob_start. But the latter has to be called before the first output, so ideally in the first line of the script that’s initially called.

Answer 5

As already mentioned by the others use ob_start() or the output_buffer-setting to buffer the output. Apart from that it's from my point of view not a good practice to output content in the middle of functional code but this is a another topic.

You can find more information at Google or in this Article about Output Buffering in PHP.

Answer 6

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');
?>