PHP in PHP

Hello ! I want to offer 2 possebiliys to watch my pages: - with frames (the menus are in a frame) - without frames (the menus are above every page) The structure with frames is ready-to-go and online since 2 years. This are 90% htm-pages and I do not want to change it into .php because I got them into a lot of search-engines. The idea now was to take a page, parse it through a php script (add the menus and change all links and so on) and then put it out. I made something like shop.php?page.htm to do this, which loads page.htm, parse it, changes all linkk into shop.php?... and print it out. This works fine. The problem: I got some php-pages, so I got to call shop.php?page.php. When now loading the page.php, I got the php-code and not the php-output of page.php. How can I get a PARSED version of page.php as a string ? Regards Martin