variables not passing at all

Hi. I am very new to PHP. I have both apache and mysql as well as php installed on my laptop. I thought PHP was functioning correctly because when I do a phpinfo() I get the appropriate diagnostic page. However in a couple of exercises designed to display variables populated from a form in one case, and in the other, a very simple page to just display the contents of a few of the built-in HTTP variables such as HTTP_REFERER, the variables aren't passing. The pages where the variable contents should display are empty. I've had a friend try the code on their server and they work fine so I know it's not my code which leads me to server configuration. Any ideas? I"m really stumped. TIA - Matt