How do I parse my .html files as PHP?

[Wulk]

I know this question has been asked 2 times here, and I have been googling and testing for a couple of hours now but was not able to find a solution.
I'd like to make my .php files look as if they were .html files.

Since Dathorn servers are running running PHP as CGI with suEXEC, adding
AddType application/x-httpd-php .html
to the .htaccess is not an option and leads to nothing but the unpretty 500 server error.

So parsing .html files as PHP probably has to be done with a php.ini - right?

How do I have to alter my php.ini in order to get these servers here to parse .html files like .php files?

[bjacobs]

Add AddHandler application/x-httpd-php .php .shtml .html .htm to your htaccess file in your main folder.

[Wulk]

main folder - that's it, thanks!

I tried to do that with the .htaccess file of a subdomain for testing - which does not work.