This may help. Since the PHP control flow is passed to your code, if you're ever not sure about what content is actually being made available, you can just stop processing and examine it's contents. Try adding this to your rule:
Then put through a submission or update a submission (depending on which event(s) you have associated your rule with).
That will display everything you're receiving. For this module, all POST keys are editable - and of course, you can add your own. Any other variables you create are ignored.