note 55900 added to ref.session

I am trying to maintain a users logged in state over multiple sites. We have 3 seperate sites on 3 different hosts.Each site will be have the same header for global navigation just different content. I am wanting to allow a user to login once and be able to go between each site, without logging in again. Once they logout I then not want them to be able to access any of the 3 sites without logging in again. Any thoughts on the matter? ---- Manual Page -- http://www.php.net/manual/en/ref.session.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+55900 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+55900&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+55900&report=yes Search -- http://master.php.net/manage/user-notes.php