how cookies simultaneously work for both url one with www. and one does not
cookies treat not the same with:
http://www.sample.com VS http://sample.com
how to make one single cookies work for both?
That's how cookies work. If you want them to work across subdomains then you need to create them with a domain of ".sample.com". Coppermine doesn't have a cookie domain setting however.
Use a custom .htaccess file that takes care of the leading www subdomain to go out of harm's way.
To always use the leading www subdomain, use something likeRewriteEngine On
RewriteCond %{HTTP_HOST} ^domain.com
RewriteRule (.*) http://www.domain.com/$1 [R=301,L]
To always redirect from the leading www subdomain to just the domain, use something likeRewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.domain\.com$ [NC]
RewriteRule ^.*$ http://domain.com%{REQUEST_URI} [R=301,L]If you need details on that technology, google for it, as this is not related to coppermine.