fnmatch() checks if the passed string would match the given shell wildcard pattern.
This is especialy useful for filenames, but may also be used on regular strings. The average user may be used to shell patterns or at least in their simplest form to '?' and '*' wildcards so using fnmatch() instead of ereg() or preg_match() for frontend search expression input may be way more convenient for non-programming users.
See also glob(), ereg(), preg_match() and the unix manpage on fnmatch(3) for flag names (as long as they are not documented here ).