MogileFS::FID(3)

NAME
MogileFS::FID - represents a unique, immutable version of a file

ABOUT
This class represents a "fid", or "file id", which is a unique revision of a file. If you upload a file with the same key ("filename") a dozen times, each one has a unique "fid". Fids are immutable, and are what are replicated around the MogileFS farm.