My PhpStorm (version 7.0) understands the fluent interface without PHPDocs (because of `return $this` in the Varnish class `purge`, `ban` and `refresh` methods). When I add `@return BanInterface $this` to the BanInterface's PHPDoc, PhpStorm only sees the `ban` method on the Varnish class, which is not what we want. So I think `@return $this` is best, for what we return is not a `BanInterface` per se, but the HTTP cache class implementing it (Varnish), with all its additional methods.