include and include_once inheritance

Hello, I've got a page that uses include_once to include a set of functions for use in that page. I later have another include_once pulling in another page, which generates a table. It relies on a function from the first file, yet an error is being generated undefined function, I thought that since the function was included in the main page, and that since the table file was also being included in the main page that the functions would also be available to the table file. Is this not so? Thanks. Dave.