From mediawiki.org
This page is a translated version of the page Manual:$wgCookieDomain and the translation is 29% complete.
Cookies: $wgCookieDomain
Explicit domain for login cookies.
Wprowadzono w wersji:before 1.1.0
Usunięto w wersji:nadal w użyciu
Dozwolone wartości:(string)
Domyślna wartość:''


Set to an explicit domain on the login cookies, e.g. thissubdomain.mydomain.org or .mydomain.org for all your subdomains.

By default this isn't set, so php's setcookie function will just set a cookie on the current domain. This is a bad thing if e.g. your site is available from both www.example.com and example.com, since users that log into the former will be logged out as soon as they visit the latter.