If you are using mod_autoindex to list your directory contents on the web, you may want to add header and footer using HeaderName and
However, if you refer to .php scripts in these directives, they are
either ignored or listed as plain text(php source).
In order to have HEADER.php really executed, you need to add in your httpd.conf some code like:
AddType text/html .php
AddHandler application/x-httpd-php .php