I took a quick look at your account. I suspect that the problem may be due to large number of Contact Lists in your account. I did not look at code behind our sample PHP script, but I suspect that it is only looking at the first page (50 lists) of contact lists returned by the API. Can you run a quick test with another list in your account (a list which has been around for a while) and see if the script works?
Tom M Group Product Manager – Content Editing Constant Contact