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function is not described

get_the_category_rss() WP 2.1.0

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.

Hooks in function
Return

String. All of the post categories for displaying in the feed.

Usage

get_the_category_rss( $type );
$type(string)
Optional.
Default: type returned by get_default_feed()

Code of get the category rss: wp-includes/feed.php WP 5.2.2

<?php
function get_the_category_rss( $type = null ) {
	if ( empty( $type ) ) {
		$type = get_default_feed();
	}
	$categories = get_the_category();
	$tags       = get_the_tags();
	$the_list   = '';
	$cat_names  = array();

	$filter = 'rss';
	if ( 'atom' == $type ) {
		$filter = 'raw';
	}

	if ( ! empty( $categories ) ) {
		foreach ( (array) $categories as $category ) {
			$cat_names[] = sanitize_term_field( 'name', $category->name, $category->term_id, 'category', $filter );
		}
	}

	if ( ! empty( $tags ) ) {
		foreach ( (array) $tags as $tag ) {
			$cat_names[] = sanitize_term_field( 'name', $tag->name, $tag->term_id, 'post_tag', $filter );
		}
	}

	$cat_names = array_unique( $cat_names );

	foreach ( $cat_names as $cat_name ) {
		if ( 'rdf' == $type ) {
			$the_list .= "\t\t<dc:subject><![CDATA[$cat_name]]></dc:subject>\n";
		} elseif ( 'atom' == $type ) {
			$the_list .= sprintf( '<category scheme="%1$s" term="%2$s" />', esc_attr( get_bloginfo_rss( 'url' ) ), esc_attr( $cat_name ) );
		} else {
			$the_list .= "\t\t<category><![CDATA[" . @html_entity_decode( $cat_name, ENT_COMPAT, get_option( 'blog_charset' ) ) . "]]></category>\n";
		}
	}

	/**
	 * Filters all of the post categories for display in a feed.
	 *
	 * @since 1.2.0
	 *
	 * @param string $the_list All of the RSS post categories.
	 * @param string $type     Type of feed. Possible values include 'rss2', 'atom'.
	 *                         Default 'rss2'.
	 */
	return apply_filters( 'the_category_rss', $the_list, $type );
}