apigiility file upload output

gistfile1.txt

The $data var in POST (create) returns:
stdClass Object
(
  [field_name] => slide_image
  [file_type] => image/jpeg
  [file_resize] => {"width":900,"height":700}
  [name] => aaa
  [caption] => aaa
  [slideshow_id] => 53501394499c13a204d63af2
)

whereas the same $data var (after adding the multipart/form-data) in PUT (update) returns the Request Payload:
stdClass Object
(
  [------WebKitFormBoundary6jWImBh90tl8U2YC
Content-Disposition:_form-data;_name] => "field_name"

slide_image
------WebKitFormBoundary6jWImBh90tl8U2YC
Content-Disposition: form-data; name="file_type"

image/jpeg
...
------WebKitFormBoundary6jWImBh90tl8U2YC
Content-Disposition: form-data; name="slide_image"; filename="jpg-1280x1024_hd-forty-eight.jpg"
Content-Type: image/jpeg