X-Sendfile directory permissions on Cpanel? PHP

Hi

I'm not sure if this is a Cpanel one or not, but I am getting stumped and running out of options. Hopefully someone here may have some ideas.

We have a dedicated server with WHM access, and our host takes care of the server admin. Nobody else has access to the server.

We have set up a first site in WHM, Site A. Above the public_html in the top directory for this site, we have put a shared directory. This directory contains scripts etc that other sites on the server need to access - but at the same time not allow public access.

Now we have set up Site B on the same server. If I run a force download test script on Site B (using an absolute path), it can access and serve the file on Site A with no problems.

If I run a test XSendfile script on Site A, accessing the shared directory also (but on the same account), it will serve the file with no problems.

The problem occurs when I try to use XSendfile on Site B, to send the file on Site A.

It seems that PHP has access to the files in another site/account. I just don't see why XSendfile does not.

Could this be some kind of cpanel permissions issue, or a general permissions issue, or something else perhaps?

If anyone has any ideas your help would be very appreciated.

Thanks.