Message Interfaces, Classes and Traits MessageInterface HTTP messages consist of requests from a client to a server and responses from a server to a client. This interface defines the methods common to each. RequestInterface Representation of an outgoing, client-side request. ResponseInterface Representation of an outgoing, server-side response. ServerRequestInterface Representation of an incoming, server-side HTTP request. StreamInterface Describes a data stream. UploadedFileInterface Value object representing a file uploaded through an HTTP request. UriInterface Value object representing a URI.