get_the_category_rss( string $type = null ): string
- Since
- 2.1.0
- Source
wp-includes/feed.php:381
Description
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.
Compatibility
- WordPress
- since 2.1.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Parameters
$typestringoptional- Optional, default is the type returned by get_default_feed().Default:
null
Return value
string- All of the post categories for displaying in the feed.
Performance profile
How much work a call to get_the_category_rss() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Heavy
- Scaling
- Scales with input
- Instructions
- 30–43
- Plugin surface
- 1 hook
- Called by
- 1
Reads stored settings via get_option(), cached per request but not free on a cold cache.
The body loops, so the work grows with what you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 108.
Third-party callbacks on 'the_category_rss' run inside this call, and their cost is not bounded by anything here.
1 place in core call this, so the cost is paid more often than your own code shows.
What it touches
- optionoption read or write
get_option()called directly - hookthird-party callbacks
apply_filters()called directly - cacheobject cache
wp_cache_get()one call below get_the_category_rss() - serializeserialisation
maybe_unserialize()one call below get_the_category_rss()
Further down the call graph this can also reach query and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.
What one call costs · 2 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost get_the_category_rss() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
!empty($type) | 30–40 | get_the_category(), get_the_tags(), array_unique(), apply_filters() |
empty($type) | 33–43 | get_default_feed(), get_the_category(), get_the_tags(), array_unique(), apply_filters() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 108 instructions, 30–43 executed per call, 12 branches. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Hooks and filters fired · 1
One hook fires while get_the_category_rss() runs, in this order:
- apply_filters( the_category_rss )filterline 428 (+47 into the body)
Filters all of the post categories for display in a feed.
Uses · 8
- get_default_feed()Retrieves the default feed.
- get_the_category()Retrieves post categories.
- get_the_tags()Retrieves the tags for a post.
- sanitize_term_field()Sanitizes the field value in the term based on the context.
- esc_attr()Escaping for HTML attributes.
- get_bloginfo_rss()Retrieves RSS container for the bloginfo function.
- get_option()Retrieves an option value based on an option name.
- apply_filters()Calls the callback functions that have been added to a filter hook.
Used by · 1
- the_category_rss()Displays the post categories in the feed.
Source code
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 );}Changelog
Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.0.4 tag, from
src/wp-includes/feed.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.