When Click a HyperLink, Promp password before Showing the Page

Dear all Can someone pls tell me how i can make a behavior in php which when a user click on a hyperlink, then a page for login will appear first and then once the username and password is right, the page of which user aiming to browse will show, otherwise a error message will tell the user that the username or password ar not correct. I know it will be easy if there is only one hyperlink, but what happen if there are many of them? Thx very much Jack jack@nedcor.com