Sorry, for wasting space/time. I just read the sticky about the $_GET etc.
hmm that's weird because there doesn't seem to be a problem with your coding as I just tested it 😕
Try putting this as your form line:
<form action=\"\" method=\"get\" name=\"form2\">
providing you are submitting to the same page?
No worries. I figured it out. You have to use: $_GET['admin'] to access the variable. Just read the sticky.