phpFlickr Caching to Filesystem or MySQL?

Question

Are you supposed to be able to see distinct filenames via phpFlickr's caching to filesystem or MySQL? I've set the parameters as listed in the readme, but caching does not seem to generate any files or mysql table rows.

I've tried both the filesystem (chmod 777 in cache folder) and mysql method (manually created cache table). Any advice on what's to be done to enable caching on phpFlickr ? http://phpflickr.com/docs/caching/

$f = new phpFlickr($key);

$f->enableCache("db", "mysql://user:password@localhost/database");