Ive just started using smarty. I have a question about it.

Im currently using a header template to put the header content in each page. So if i have a script called registration.php and an associated template called registration.tpl.html i include the header as usual:

PHP Code:
{include file="header.tpl.html"} 
Now i have logic in this header.tpl.html which is assigned in a file called header.php. Problem is if access registration.php the header get loaded but its logic is not parsed.

How do i include files such as header.tpl.hml and also make the logic within them get output?