How can I determine the maximum filename length on a linux box?
Preferred in PHP programming language.
You want pathconf or fpathconf, which are not exposed (yet) in PHP. (When they are, they'll probably be posix_pathconf.)
You may also shell out to getconf, a command-line utility interface to the same functionality. Try this on your system:
$ getconf NAME_MAX /tmp
$ getconf PATH_MAX /tmp