Url Links not working properly

Hi Team,

I am trying to customise a zencart and have come accross an unusual problem:

My url on my links are showing up as:
http://www.my_domain.com/folder/www.my_domain.com/folder/indexphp?main_page=contact_us

My configure.php has:

  define('HTTP_SERVER', 'www.my_domain.com');
  define('HTTPS_SERVER', 'www.my_domain.com');
  define('DIR_WS_PLANNER', '/folder/');
  define('DIR_WS_HTTPS_PLANNER', '/folder/');

and my links in the header:

<li><a href="<?php echo zen_href_link(FILENAME_CONTACT_US, '', 'SSL'); ?>"><?php echo HEADER_TITLE_CONTACT_US; ?></a></li>

zen_href_link in html_output_php:

function zen_href_link($page = '', $parameters = '', $connection = 'NONSSL', $add_session_id = true, $search_engine_safe = true, $static = false, $use_dir_ws_planner = true) {
    global $request_type, $session_started, $http_domain, $https_domain;

Where would it duplicate part of the URL?
Where else should I look, is there a function I could have altered?

You need to have "http://" and "https://" in the HTTP_SERVER and HTTPS_SERVER settings, respectively.
If you leave those as just starting with "www.", then you'll get the symptoms you're reporting.

Thanks Dr Byte,

Works great now.

Goshawk