<?php

   function authenticate_user() {

      header('WWW-Authenticate: Basic realm="Secret Stash"');

      header("HTTP/1.0 401 Unauthorized");

      exit;

   }

   if(! isset($_SERVER['PHP_AUTH_USER'])) {

      authenticate_user();

   } else {

      mysql_connect("localhost","authenticator","secret") or die("Can't connect to database server!");

      mysql_select_db("gilmorebook") or die("Can't select authentication database!");

      $query = "SELECT username, pswd FROM user WHERE username='$_SERVER[PHP_AUTH_USER]' 

                      AND pswd=MD5('$_SERVER[PHP_AUTH_PW]') AND ipAddress='$_SERVER[REMOTE_ADDR]'";

      $result = mysql_query($query);

      if (mysql_num_rows($result) == 0)

         authenticate_user();

         mysql_close();

      }

?>