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.
Note: 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:
path - path were the file got stored
size - size of the stored file in bytes
type - mimetype if given in the FDF