I used the function described in the following URL to create some zip files programatically which turned out to be working wonderful on the development site:
http://davidwalsh.name/create-zip-php .
Thing is, when I uploaded the website to the production server, the file created seemed to be corrupted. winrar has given me "unexpected end of archive" error. the archive could be fixed by winzip tools, so obviously all the data is in there. I'd like to know why such thing should happen, and how can i fix it ?