This contains the file name extension of the file uploaded. If a
file name extension is not available it may be derived from other
The returned value includes the period character of the
extension, such as ".jpg" or ".txt".
Not all platforms use file name extensions so in these cases
other information may be used to identify the type of file.
If files are uploaded from MacBinary capable Macintosh browsers
(Internet Explorer but not Netscape Navigator) the upload contains
information on the Macintosh Creator and Type. This information may
be used to infer the file type of the uploaded document. The
inference is based firstly on the Services for Macintosh (SFM)
settings which can be altered using MacFile. If SFM is not
installed or does not provide a suitable match then a heuristic
approach is used.
In some cases no file type information will be available. In
these cases an empty string will be returned.