variables not being passed from form ??

I have a web page which contains a form whose action is a php script. Unfortunately, NONE of the form's variables are being passed when the form is submitted. For example: the submit button's name is 'submit', and the value is 'Add', but in the receiving php script, $submit is empty, and so is $HTTP_POST_VARS["submit'] register_globals is On The form method is post. What else am I missing?