class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
more info about the class
$filename = $_FILES['file']['name'];
echo "FILENAME : ". $filename;
Actually returns the correct filename.
So instead of tryin XMLHttpRequest (that I have not managed to get working), could I just use command like:
$handle->file_dst_name_body = 'test';
Which the upload class seems to ignore.