How To Have .html Treated As .php

I have several websites running on Linux hosting with cPanel, that were developed as static .html files, where for ease of maintenance (use of includes) and future improvements I want the pages treated as .php. On one server I use, I just put:

AddHandler application/x-httpd-php .html .shtml

into the .htaccess file and the pages were treated as .php, exactly what I wanted.

The other sites are on a cPanel reseller account at iVhosting.com. When I tried this there, it didn't work. I tried some other ideas suggested by Google, which resulted in the .php files being downloaded as text files. I contacted iVhosting support, who stated: "you will not be able to do this on our server since we use phpsuexec/suphp for more security. PHP pages have to have .php extension."

So what can I do? I can't rename the pages all to .php because this would break incoming links and destroy the page's PR. Creating a permanent redirect for each page to the same name with .php extension would create a very large .htaccess and be extremely tedious to do.