PPTX corrupted when uploading in php (chunk)

Uploading a 'pptx' file divided into parts through the Dropbox API is corrupted.
Does anyone have a solution to this problem?
Thank you

 

 

$dropboxAdapter = new DropboxStorageRepository();
$file = $request->file("file");
$chunk = (int) $request->get('chunk', false);
$chunks = (int) $request->get('chunks', false);
$originalName = $request->get('name');
$dir_move = utf8_encode ($request->headers->get("current-dir"));

if($chunk == 0){
     $id = $dropboxAdapter->client->chunkedUploadStart(File::get($file));

     session::forget("fid");
     session::forget("bof");
     Session::set("fid", $id);
     Session::set("bof", $file->getSize());
}
if($chunk > 0 && $chunk < $chunks - 1){

     $bytesOffset = Session::get("bof");
     $id = Session::get("fid");
     $dropboxAdapter->client->chunkedUploadContinue($id,$bytesOffset,File::get($file));
     Session::set("bof",$bytesOffset+$file->getSize());

}
if ($chunk == $chunks - 1) {
    $bytesOffset = Session::get("bof");
    $id = Session::get("fid");
    $dropboxAdapter->client->chunkedUploadContinue($id,$bytesOffset,File::get($file));

    $file_dropbox = $dropboxAdapter->client->chunkedUploadFinish($id,$dir_move."/".$originalName,WriteMode::force());
/
    $saveFile = $this->SaveFile($file_dropbox);
    session::forget("fid");
    session::forget("bof");
}