WordPress Version: 6.2
/**
* Adds a new feed type like /atom1/.
*
* @since 2.1.0
*
* @global WP_Rewrite $wp_rewrite WordPress rewrite component.
*
* @param string $feedname Feed name.
* @param callable $callback Callback to run on feed display.
* @return string Feed action name.
*/
function add_feed($feedname, $callback)
{
global $wp_rewrite;
if (!in_array($feedname, $wp_rewrite->feeds, true)) {
$wp_rewrite->feeds[] = $feedname;
}
$hook = 'do_feed_' . $feedname;
// Remove default function hook.
remove_action($hook, $hook);
add_action($hook, $callback, 10, 2);
return $hook;
}