Permissions on a mounted NFS share

I am trying to make a php script on a webserver write into a folder /data on a fileserver. Apache 2.2, PhP 5.x. It's just a test configuration but I'd like to understand the thing somehow as I am not very experienced regarding permissions when it comes to webservers. I am sharing the folder /data on the fileserver by adding /data 192.168.20.6(rw,sync,no_subtree_check) Mount the folder by sudo mount 192.168.20.5:/data /mnt/data Create a link to the webroot(does that makes sense at all?) sudo ln -s /mnt/data /webroot/site1/share Then I get this: Warning: fopen(/webroot/site1/share/data/uploads/Fotoraum/Original/Bluehend/test.txt): failed to open stream: Permission denied Where and how do I have to adjust permissions in a sane manner to allow the script to write into /data and its subfolders? Thanks a lot!