It's possible to run a PHP (or SSI code ) file as a regular HTML file in a folder, or in a whole account, by editing the .htaccess file and adding this code:
To run a PHP as an HTML:
AddType application/x-httpd-php5 .html .htm .php
AddHandler application/x-httpd-php5 .html .htm .php
To run a SSI code as an HTML:
AddHandler server-parsed .html .htm