How to fetch answer category on the answer detail form

Summary:

I need help in fetching answer category on the answer detail form.

Content (required):

We have setup categories, associated products and corresponding answers. In the customer portal we are trying to display answers based on the category selection. Category is identified based on a query string. This works if the user navigates to the list page using query string. But if the user navigates to an answer detail page directly without a query string, we need a way to identify the answer's category. We then store the category as a cookie and use it further.

I need help in identifying proper approach to fetch answer category and populate a php variable on the detail page.