Add PHP to HTML files with .htacess

For web servers using PHP as apache module:

AddType application/x-httpd-php .html .htm

For web servers running PHP as CGI:

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

In case you wish to do the ASP mimick:

For PHP as module:

AddType application/x-httpd-php .asp

OR

For PHP as CGI:

AddHandler application/x-httpd-php .asp