Windows fields are in a "WINXP" section (the format I don't know), but they are also elsewhere including "comments" & "subject" in null terminated "UTF-16LE" format, this code work for me:

...
$PhotoInfo->Comments    = GetPhotoValueWindows16Bit($IDFO, 'Comments');
$PhotoInfo->Subject     = GetPhotoValueWindows16Bit($IDFO, 'Subject');

 function GetPhotoValueWindows16Bit(&$Array, $Index)
 {
        $Value16 = GetPhotoValue($Array, $Index);
        if  ($Value16 === null)
            $R = null;
        else
        {
            $R = iconv('UTF-16LE', 'UTF-8', $Value16);      //Still ends in a null byte
            $R = str_replace("\x00", '', $R);               //Remove trailing null (but handle any).
        }
        return $R;
    }