<?php
if (!isset($_SERVER['PHP_AUTH_USER'])) {
   header('WWW-Authenticate: Basic realm="My Realm"');
   header('HTTP/1.0 401 Unauthorized');
   echo 'Text to send if user hits Cancel button';
   exit;
} else {
   echo "<p>Hello {$_SERVER['PHP_AUTH_USER']}.</p>";
   echo "<p>You entered {$_SERVER['PHP_AUTH_PW']} as your password.</p>";
}
?>