Extracts a file uploaded by means of the "file
selection" field fieldname
and stores it under
savepath. savepath
may be the name of a plain file or an existing directory in
which the file is to be created under its original name. Any
existing file under the same name will be overwritten.
注: There seems to be no other way to find out the original filename but to store the file using a directory as savepath and check for the basename it was stored under.
The returned array contains the following fields: