that function should be defined in the WA_DigitalFilePro/HelperPHP.php file.
it may be that your copy has become corrupted. Here is a fresh copy of that file for you to upload to your server.
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.