I want to add directory to archive

Hey!

I use method appendFiles, but I have only files in zip archive. I want to see directory in archive.

i.e.

I have files in directory_name:

-directory_name
--123.txt
--321.txt

appendFiles("directory_name", true);

I want to get in archive:

-directory_name
--123.txt
--321.txt

but I only get files:

--123.txt
--321.txt

Please, help. :) Sorry for my bad english.

Thanks