If you have root access to the server then you should be able to modify the
AddType application/x-httpd-php .php .htm .html
directive in the httpd.conf file to include the extensions you want.
If you do not have root access to this file then you can create an .htaccess file in your web root with the AddType line in it just like above.
This is a pretty cool feature of Apache, as you can override a lot of the default directives on a per directory basis.