Giving access to user based on security level

hey folks,
i have a web app made. its in php and menu is all based on css ul and li’s. now a thing has come up. each user will have different level of access. some might have full, some can view each page and some very little pages. problem comes with the naming of the page.
suppose my app has four modules,

  1. index.php
  2. Schedule.php
  3. graph.php
  4. technical.php
    now this user say abc has access to the tab 3 and 4 namely graph.php and technical.php, when the person click on the side menu which is the main link to going into that module, clicks on it. by default landing page is index.php but what as the user privillages only allow him to see graph.php and technical.php. having said that, how can i make the 3rd page as a landing page. as index.php is already given to index.php and i don’t want to expose him to directory structure. what should i do to make this concept work?
    is it possible?