Is $KT_rsUser->Fields an array? If so, your line should read:
$KT_rsUser->Fields['user_id'] = $KT_valUserID;
Or if you need all the variables in that array:
extract($KT_rsUser->Fields, EXTR_PREFIX_ALL, 'KT_val');
This will give you a variable for each element in the array. All will look like this: $KT_valArrayKeyName