Make sure that there is an include that looks like this near the top of the page:
<?php
//WA Database Search Include
require_once("WADbSearch/HelperPHP.php");
?>
The FilterDef class is defined in that file.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.