Fixes For PHP Code

I have some link rotation code in php, the file is attached that works somewhat but I need some changes to make it work for what I need it for. I want to use this script to evenly rotate through affiliate offers and landing pages. The first problem I am having is that the links don't seem to rotate evenly and sometimes not at all. The second problem I am having is that I plan to, at times, use links that redirect through my tracking script first. When I put a link in that redirects through my tracking script, like this one ([login to view URL]) I get an internal server error and it won't redirect. The third issue is the links seem to open in an iframe instead of redirecting. So if I enter the urls to google and yahoo into this code, google or yahoo url won't show up in the url bar when I visit the link. If you can fix these or come up with something else that would be great.