2020-05-01 / 4660阅 / 悠然
Retrieve all of the post categories, formatted for use in feeds.
All of the categories for the current post in the feed loop, will be retrieved and have feed markup added, so that they can easily be added to the RSS2, Atom, or RSS1 and RSS0.91 RDF feeds.
default is the type returned by get_default_feed().
Default value: null
(string) All of the post categories for displaying in the feed.