best use of https?

hello there.

for the first time i'm using https to post a form with credit card details. So i've placed the form in /https/

However the whole site uses absolute paths for PHP like;
include_once($_SERVER['DOCUMENT_ROOT']."/scripts/php/general.php");

and relative href paths in the main navigation like /about/contact/ which obviously wont get files from the /httpdocs/ directory

so all the corresponding links don't work! And i have to create a new set of files just to be included with the one form.

Seems really messy and was wondering if there's an easier way to post the form on https without having to nearly duplicate the site on the /https/ ?

any pointers welcome, Dan.

use mod rewrite to redirect all pages except those you need to to be https

ok -thanks for the tip...

so i can keep all my files in httpdocs but use a .htaccess to make it secure?

so if this was the current rule how could i make it https?
RewriteRule ^{purchasing-process/} purchasing-process.php [L]

any reference much appreciated!

Dan.