What is PHP Safe Mode GID?

Question

According to the PHP Safe Mode Docs on safe_mode_gid:

By default, Safe Mode does a UID compare check when opening files. If you want to relax this to a GID compare, then turn on safe_mode_gid. Whether to use UID (FALSE) or GID (TRUE) checking upon file access.

To a PHP script running on a web server, what is the difference between a UID (User Identifier) check and a GID (Group identifier) check?

Answer 1

This will just allow you a little more flexibility in your web server setup. Using safe_mode_gid, you should be able to run individual PHP/httpd processes for each user on your system, but give each process the ability to read some shared files as long as they are all run as the same group (GID) and the shared files are owned by this group.