Returning the filename from a save as dialog

How to a get the filename from a header("Content-Disposition: attachment; filename=" . $fileName); if it´s changed in the save as-dialog of the user

not really sure what you mean here,

once the user downloads using 'save as', if they change the name of the file there is no way track what they changed it to, if thats what your asking??

thz, that answered the question