nanoFTPd is an ftp daemon written in php. as of version 4.2.0, php supports the command-line interface (stable since 4.3.0), which nanoFTPd relies on. nanoFTPd is modular, so itâ€™s easy to add custom modules and other stuff, like different database interfaces (currently supports mysql and postgresql).
Features of the app include user authentication via a database or text file, dynamic IP support, and most of the usual FTP goodies you're used to in a server. You'll need at least PHP 4.2.0 to get it up and running, but configuration is simple and installations it just as easy. You can grab the software from their website.