$demo->setFileUpload("fldFilename");
$demo->onFileUploadExecuteCallBackFunction("uploadDocument");

function uploadDocument($array){
  $id         = $array[id];  //this will always be the value
  $id         = $array[pkID]; //same as above IF the pk is pkID
  $fileName   = $array[fileName];
  $fileSize   = $array[fileSize];
  $fileType   = $array[fldType];
  
  if ($fileName != ''){
    $success = qr("UPDATE tblDemo SET fldFilesize = '$fileSize'
                                  WHERE pkDemoID = $id");
  }
}