set_cookie not setting cookie

[eluser]internut[/eluser]
i'm able to grab the cookie, just not set it. I'm grabbing it using. Maybe it does have something to do with the order of things. I'm working in an admin area right now but if you want to reply with the XSS clean code that'd be cool for future reference for me and others.

Grabbing cookie via CI using:

Code:

$var = get_cookie('var');