PHP and .HTACCESS

I am new to learning PHP and have learned a lot over the last few weeks. One thing that I can not find anywhere is how to code it so a user can click logoff and have it route them to another page and remove their authentication that was set. ie... I user goes to www.mysite.com and clicks on a link called STAFF The STAFF.mysite.com is protected with authentication using .htaccess The staff enters their ID and Password and is allowed in. I want to have a button that says LOGOFFF that will remove the authentication I know how to do the header(location... to route them back to another page, but I have not been able to remove the authentication so it will ask them for their password again when they return to staff.mysite.com I have even tried: header('WWW-Authenticate: Negotiate'); header('WWW-Authenticate: NTLM', FALSE); but no go... Thanks in advance!! Jim