This class can backup local files as a ZIP archive sent to Dropbox
It handles the OAuth authorization process to obtain a token to access an API on behalf of the current Web user.
The class create a ZIP archive with files from a directory to backup.
The ZIP archive is sent to the DropBox server using requests sent to is API.
http://www.phpclasses.org/package/8922-PHP-Backup-local-files-as-a-ZIP-archive-to-Dropbox.html