add these lines to the httpd.conf or .htaaccess :
AddType application/x-httpd-php .html
AddType application/x-httpd-php .htm
restart apache and now you can use PHP code in HTM\HTML files like this :
<?php echo 'Hello World'; ?>Integrating PHP in HTML files (Apache configuration)
9. We’re a group of volunteers and starting a new scheme in our community. Your web site provided us with valuable information to work on. You have done a formidable job and our entire community will be grateful to you.