wp_get_post_categories( int $post_id = 0, array $args = array() ): array|WP_Error

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$post_idintoptional

The Post ID. Does not default to the ID of the global $post. Default 0.Default: 0

$argsarrayoptional

Category query parameters. Default empty array.
See WP_Term_Query::__construct() for supported arguments.Default: array()

Return value

array|WP_Error

List of categories. If the $fields argument passed via $args is 'all' or 'all_with_object_id', an array of WP_Term objects will be returned. If $fields is 'ids', an array of category IDs. If $fields is 'names', an array of category names.
WP_Error object if 'category' taxonomy doesn't exist.

Performance profile

How much work a call to wp_get_post_categories() 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

Reaches the database via wp_get_object_terms().

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

17

Executed per call on PHP 8.5. The body compiles to 17.

Plugin surface

None

Nothing here hands control to plugin code.

Called by

9

9 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• querycontent querywp_get_object_terms()called directly
• hookthird-party callbacksapply_filters()one call below wp_get_post_categories()

Further down the call graph this can also reach option, cache, serialize 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 · 1 distinct outcome

One number would be a lie: the work depends on which branch runs. These are every distinct cost wp_get_post_categories() can have, taken from its control-flow graph on PHP 8.5.

Uses · 2

• wp_parse_args()Merges user defined arguments into defaults array.
• wp_get_object_terms()Retrieves the terms associated with the given object(s), in the supplied taxonomies.

Used by · 9

• bulk_edit_posts()Processes the post data for the bulk editing of posts.
• wp_get_post_cats()Retrieves a list of post categories.
• wp_xmlrpc_server::_prepare_page()Prepares page data for return in an XML-RPC object.
• wp_xmlrpc_server::blogger_getPost()Retrieves a post.
• wp_xmlrpc_server::blogger_getRecentPosts()Retrieves the list of recent posts.
• wp_xmlrpc_server::mt_getPostCategories()Retrieves post categories.
• wp_xmlrpc_server::mt_publishPost()Sets a post's publish status to 'publish'.
• wp_xmlrpc_server::mw_getPost()Retrieves a post.
• wp_xmlrpc_server::mw_getRecentPosts()Retrieves list of recent posts.

Source code

View on Trac ↗View on GitHub ↗

4405function wp_get_post_categories( $post_id = 0, $args = array() ) {4406	$post_id = (int) $post_id;4407 4408	$defaults = array( 'fields' => 'ids' );4409	$args     = wp_parse_args( $args, $defaults );4410 4411	$cats = wp_get_object_terms( $post_id, 'category', $args );4412	return $cats;4413}

Changelog

Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/post.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

Corrections

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