Do you need to parse both SSI and php in the page? If so, you would require apache2 which can do that with the addition of a handler. I don't quite remember which order pages are parsed in, but, I believe you set it to parse .php first, then, AddOutputFilter INCLUDES
If you are running apache2, and want to parse .shtml pages for php only, the following will do that:
Code:
RemoveHandler .shtml
AddType application/x-httpd-php .shtml
If you are running apache1, I believe the above should work. If your host is running fastcgi, it might not react the same way and then you need to get them involved.