Should I implement both RequestInterface and ServerRequestInterface

Question

I am currently writing an implementation of the HTTP Message Interface Recommendation (PSR-7) for my personal PHP framework. I've written classes for each interface in the recommendation. But now I realize that I do not need an abstraction for outbound requests.

At the moment I have:

• Message for MessageInterface,
• Request for RequestInterface,
• Response for ResponseInterface,
• ServerRequest for ServerRequestInterface,
• Stream for StreamInterface,
• UploadedFile for UploadedFileInterface, and,
• Uri for UriInterface.

I wonder if I must implement every interface of the recommendation to claim my framework uses it? Or may I only implement the parts of I need?