PHP header location-redirect doesn't work - why?

Here's my file. I want to make it redirect, but nothing happens. To check out what is going on, I added an echo before the header part.

It neither throws an error or redirect to index.php. What is wrong?
I have turned output buffering on/off, but nothing makes it redirect. What can I do?

error_reporting(E_ALL);
echo 'This is an error';


header("Location: login.php");
die();
?>

Thanks

Answer

I reminded myself that I had xDebug installed on the actual test environment and after googling it, I found this site: http://bugs.xdebug.org/view.php?id=532

So I'll downloaded the last version of xDebug and changed the php.ini accordingly for the new file and everything works out like a charm. Headers are being sent - the redirecetion is done and errors are displayed.

Thanks everybody for your help!