Authentication

hi I am trying to secure a web site and I can get one page at a time to ask for authentication but thats it. Right now every page visited asks for a password, otherwise there is no auth on them at all. So I am wondering how to make $PHP_AUTH_USER and $PHP_AUTH_PW global so that "isset $PHP_AUTH_USER = valid user" carries over the valid user to all pages visited until a logout button is pushed. Also I can't seem to find info on how to set up apache to require passwords for directories and not just files using php without asking for the password twice. Please help, I have looked everywhere. Thanks in advance -Dave Baldwin