Check Authendicated User

Hi, I have a complaint register page in my site. The authendicated users only allowed to register their complaints. For this i used setcookie concept in "user module" file. I have an another php file to check whether either cookie has value or empty.
My concept is,
If that php file returns true then it goes to the register page. Otherwise, it goes to the login page. But it goes to login page always. Where can I set the value for cookie?

Thanks in advance...