code: protected function processUploadedFiles(FileBag $filebag)
      {
          $adapter = new LocalAdapter($this->get('kernel')->getRootDir().'/../web/media');
          $filesystem = new Filesystem($adapter);
  
          $processed = array();
  
          if ($filebag->get('files')) {
              /*
               * @var UploadedFile
               */
              foreach ($filebag->get('files') as $file) {
                  // get the unique filepath
                  $dest = $this->createUniquePath($file);
  
                  if ($filesystem->write($dest['path'], file_get_contents($file->getPathname()))) {
                      $processed[] = $dest['path'];
                  };
              }
          }
  
          return $processed;
      }
docs: gets the filebag and moves uploaded files to filesystem.
  
  @param FileBag $filebag
  
  @return array reference list of moved files