FeedNamespaceInterface

The contract every registered XML namespace handler must implement. NamespaceRegistry::get_all() silently drops anything in the benecaster_feed_namespaces filter result that does not implement it. Core pre-registers four handlers at boot in Plugin::register_feed(): ItunesNamespace, ContentNamespace, PodcastIndexNamespace and PodloveNamespace. PodcastNamespace is a deprecated filter shim, not a handler, and is never registered.

A handler whose output depends on the tier being compiled can additionally implement one of two opt-in extensions: TierAwareFeedNamespaceInterface (channel level) or TierAwareEpisodeNamespaceInterface (episode level).