<?php
  $username = 'admin';
  $password = 'letmein';

  if (isset($_SERVER['PHP_AUTH_USER']) &&
      isset($_SERVER['PHP_AUTH_PW']))
  {
    if ($_SERVER['PHP_AUTH_USER'] === $username &&
        $_SERVER['PHP_AUTH_PW']   === $password)
          echo "You are now logged in";
    else die("Invalid username/password combination");
  }
  else
  {
    header('WWW-Authenticate: Basic realm="Restricted Area"');
    header('HTTP/1.0 401 Unauthorized');
    die ("Please enter your username and password");
  }
?>