Pass variable from Controller to dynamic CSS file?

[eluser]Sven Delle[/eluser]
I need to pass a variable to a dynamic CSS file.

Can this be done in CI?

I've tried setting a $_SESSION['variable'] in the controller and call it from a CSS file (style.php with a header type of text/css), but I get nothing (and yes, I did session_start()). Does this clash with CI's built in session handling, and can I at all use CI's session in files external to the 'system'?

How do I go about this 'problem'?