Basic code to expire Drupal cookie?

PHP
1

This type of code (for example)

setcookie( 'Elgg', '', -3600, '/', '.domain.com', false, false);
setcookie( 'mybbuser', '', -3600, '/bb/', '.domain.com', false, false);

…will work for a simple multi-logout of Elgg, MyBB and other types of sites.
The same type of code:

setcookie( 'http_auth_ext_complete', '', -3600, '/d/', '.domain.com', false, false);
// setcookie( 'http_auth_ext_complete', '', -3600, '/d/', 'domain.com', false, false); 
// setcookie( 'http_auth_ext_complete', '1', -3600, '/d/', '', false, false);

…will not work on Drupal 6.x.
Note: The Drupal cookie uses ‘host’ instead of ‘domain’, neither with or without the ‘.’ or ‘’ works so far.
How can I do the same with Drupal?
Thank you.

2

I’m sure the cookie twice had “Host domain.com” and on another login used the more standard format “Domain .domain.com”

Update:
The cookie named “http_auth_ext_complete” is getting expired and I am still logged in. Drupal uses a second cookie with the session ID as the cookie name + there is a matching entry in the session database table, also.