Windows Server 2012 - 授予查看文件夹内容的权限

I have built a client and data management software for a company (PHP) and now I'd like to make folders accessible.

To clarify my need let me put up an example:

If a clients documents are being viewed my PHP script reads everything that lies in XXX/CLIENT_ID/FOLDERNAME/ and puts it out to the view.

Now my client has announced the wish to upload whole folders into clients in order to import old data.

Therefore the new request would look like XXX/CLIENT_ID/FOLDERNAME/NEW_FOLDER/

I would like to drop out a quick for them to view the folders content. As far as I remember, if you try to request an URL which is a folder and has no index.html / php file it should display the contents, whether its more folders or some other documents, shouldnt it ?

Unfortunately when I try to access that extra folder I receive a 403 Error Forbidden.