CMS question PHP Code related

I need to have some specific pages with the .ht file configured so it can read the PHP code in existing HTML pages without having the need to renaming or changing its extension.
How do I implement this when my site is configured by some CMS, and has what is called “clean” URL structure, i.e. all pages have URL’s ending in “/” instead of .html, like ForceType application /x-httpd-php?
Sever is on shared Apache hosting.
