To with Gau Frette (Symfony extension) to be able to perform also stream operations on files, can you get the little scrawny documented Stream wrapper use.
This is configured in the gaufrette.yaml:
knp_gaufrette: stream_wrapper: ~ filesystems: backup1: adapter: backup
And can then be z.B. the following mass is a csv. Write file:
$stream = fopen('gaufrette://backup1/datei.csv', 'w+'); fputcsv($stream, [1,2,3]);