Retrieves the list of categories for a post.

Compatibility layer for themes and plugins. Also an easy layer of abstraction away from the complexity of the taxonomy layer.

• wp_get_object_terms()

$post_id int Optional

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

$args array Optional

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

More Arguments from WP_Term_Query::__construct( ... $query )

Array or query string of term query parameters.

• taxonomystring|string[]
  Taxonomy name, or array of taxonomy names, to which results should be limited.
• object_idsint|int[]
  Object ID, or array of object IDs. Results will be limited to terms associated with these objects.
• orderbystring
  Field(s) to order terms by. Accepts:
  

  • Term fields ('name', 'slug', 'term_group', 'term_id', 'id', 'description', 'parent', 'term_order'). Unless $object_ids is not empty, 'term_order' is treated the same as 'term_id'.
  • 'count' to use the number of objects associated with the term.
  • 'include' to match the 'order' of the $include param.
  • 'slug__in' to match the 'order' of the $slug param.
  • 'meta_value'
  • 'meta_value_num'.
  • The value of $meta_key.
  • The array keys of $meta_query.
  • 'none' to omit the ORDER BY clause.

  Default 'name'.
• orderstring
  Whether to order terms in ascending or descending order.
  Accepts 'ASC' (ascending) or 'DESC' (descending).
  Default 'ASC'.
• hide_emptybool|int
  Whether to hide terms not assigned to any posts. Accepts 1|true or 0|false. Default 1|true.
• includeint[]|string
  Array or comma/space-separated string of term IDs to include.
  Default empty array.
• excludeint[]|string
  Array or comma/space-separated string of term IDs to exclude.
  If $include is non-empty, $exclude is ignored.
  Default empty array.
• exclude_treeint[]|string
  Array or comma/space-separated string of term IDs to exclude along with all of their descendant terms. If $include is non-empty, $exclude_tree is ignored. Default empty array.
• numberint|string
  Maximum number of terms to return. Accepts ''|0 (all) or any positive number. Default ''|0 (all). Note that $number may not return accurate results when coupled with $object_ids.
  See #41796 for details.
• offsetint
  The number by which to offset the terms query.
• fieldsstring
  Term fields to query for. Accepts:
  

  • 'all' Returns an array of complete term objects (WP_Term[]).
  • 'all_with_object_id' Returns an array of term objects with the 'object_id' param (WP_Term[]). Works only when the $object_ids parameter is populated.
  • 'ids' Returns an array of term IDs (int[]).
  • 'tt_ids' Returns an array of term taxonomy IDs (int[]).
  • 'names' Returns an array of term names (string[]).
  • 'slugs' Returns an array of term slugs (string[]).
  • 'count' Returns the number of matching terms (int).
  • 'id=>parent' Returns an associative array of parent term IDs, keyed by term ID (int[]).
  • 'id=>name' Returns an associative array of term names, keyed by term ID (string[]).
  • 'id=>slug' Returns an associative array of term slugs, keyed by term ID (string[]).

  Default 'all'.
• countbool
  Whether to return a term count. If true, will take precedence over $fields. Default false.
• namestring|string[]
  Name or array of names to return term(s) for.
  
• slugstring|string[]
  Slug or array of slugs to return term(s) for.
  
• term_taxonomy_idint|int[]
  Term taxonomy ID, or array of term taxonomy IDs, to match when querying terms.
• hierarchicalbool
  Whether to include terms that have non-empty descendants (even if $hide_empty is set to true). Default true.
• searchstring
  Search criteria to match terms. Will be SQL-formatted with wildcards before and after.
• name__likestring
  Retrieve terms with criteria by which a term is LIKE $name__like.
• description__likestring
  Retrieve terms where the description is LIKE $description__like.
• pad_countsbool
  Whether to pad the quantity of a term's children in the quantity of each term's "count" object variable. Default false.
• getstring
  Whether to return terms regardless of ancestry or whether the terms are empty. Accepts 'all' or '' (disabled). Default ''.
• child_ofint
  Term ID to retrieve child terms of. If multiple taxonomies are passed, $child_of is ignored. Default 0.
• parentint
  Parent term ID to retrieve direct-child terms of.
  
• childlessbool
  True to limit results to terms that have no children.
  This parameter has no effect on non-hierarchical taxonomies.
  Default false.
• cache_domainstring
  Unique cache key to be produced when this query is stored in an object cache. Default 'core'.
• update_term_meta_cachebool
  Whether to prime meta caches for matched terms. Default true.
• meta_keystring|string[]
  Meta key or keys to filter by.
• meta_valuestring|string[]
  Meta value or values to filter by.
• meta_comparestring
  MySQL operator used for comparing the meta value.
  See WP_Meta_Query::__construct() for accepted values and default value.
• meta_compare_keystring
  MySQL operator used for comparing the meta key.
  See WP_Meta_Query::__construct() for accepted values and default value.
• meta_typestring
  MySQL data type that the meta_value column will be CAST to for comparisons.
  See WP_Meta_Query::__construct() for accepted values and default value.
• meta_type_keystring
  MySQL data type that the meta_key column will be CAST to for comparisons.
  See WP_Meta_Query::__construct() for accepted values and default value.
• meta_queryarray
  An associative array of WP_Meta_Query arguments.
  See WP_Meta_Query::__construct() for accepted values.

Default: array()

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.

The results from wp_get_post_categories() aren’t cached which will result in a database call being made every time this function is called. Use this function with care. For performance, functions like get_the_category() should be used to return categories attached to a post.

File: wp-includes/post.php. View all references

function wp_get_post_categories( $post_id = 0, $args = array() ) {
	$post_id = (int) $post_id;

	$defaults = array( 'fields' => 'ids' );
	$args     = wp_parse_args( $args, $defaults );

	$cats = wp_get_object_terms( $post_id, 'category', $args );
	return $cats;
}