in_category( int|string|int[]|string[] $category, int|WP_Post $post = null ): bool

Checks if the current post is within any of the given categories.

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Description

The given categories are checked against the post’s categories’ term_ids, names and slugs.
Categories given as integers will only be checked against the post’s categories’ term_ids.

Prior to v2.5 of WordPress, category names were not supported.
Prior to v2.7, category slugs were not supported.
Prior to v2.7, only one category could be compared: in_category( $single_category ).
Prior to v2.7, this function could only be used in the WordPress Loop.
As of 2.7, the function can be used anywhere if it is provided a post ID or post object.

For more information on this and similar theme functions, check out the Conditional Tags article in the Theme Developer Handbook.

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Parameters

$category int|string|int[]|string[] Required
Category ID, name, slug, or array of such to check against.
$post int|WP_Post Optional
Post to check. Defaults to the current post.

Default: null

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Return

bool True if the current post is in any of the given categories.

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Source

File: wp-includes/category-template.php. View all references 

function in_category( $category, $post = null ) {
	if ( empty( $category ) ) {
		return false;
	}

	return has_category( $category, $post );
}

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Uses

Uses
Uses Description
has_category() wp-includes/category-template.php

Checks if the current post has any of given category.

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Changelog

Changelog
Version Description
2.7.0 The $post parameter was added.
1.2.0 Introduced.

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User Contributed Notes

  1. Skip to note 1 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note
    Contributed by Codex —

    Testing the current post outside the Loop
    During a request for an individual post (usually handled by the single.php template), you can test that post’s categories even before the Loop is begun.

    You could use this to switch templates like so:

    if ( in_category('fruit') ) {
	include 'single-fruit.php';
} elseif ( in_category('vegetables') ) {
	include 'single-vegetables.php';
} else {
	// Continue with normal Loop
	if ( have_posts() ) : while ( have_posts() ) : the_post();
	// ...
}

    (The Custom Post Templates Plugin allows for creation of templates for single posts. It also shows an example of how to add a template which is used for all posts in a given category, not just a single post. That example is commented out in the plugin by default but can be easily implemented by uncommenting the appropriate lines.)

  2. Skip to note 2 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 2You must log in to vote on the helpfulness of this note
    Contributed by Codex —

    Testing the current post within the Loop
    in_category() is often used to take different actions within the Loop depending on the current post’s category, e.g.

    if ( in_category( 'pachyderms' )) {
	// They have long trunks...
} elseif ( in_category( array( 'Tropical Birds', 'small-mammals' ) )) {
	// They are warm-blooded...
} else {
	// etc.
}
  3. Skip to note 3 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by revive —

    To check whether a post is within a parent category or any of it’s subcategories:

    <?php
/**
 * Tests if any of a post's assigned categories are descendants of target categories
 *
 * @param int|array $categories The target categories. Integer ID or array of integer IDs
 * @param int|object $_post The post. Omit to test the current post in the Loop or main query
 * @return bool True if at least 1 of the post's categories is a descendant of any of the target categories
 * @see get_term_by() You can get a category by name or slug, then pass ID to this function
 * @uses get_term_children() Passes $cats
 * @uses in_category() Passes $_post (can be empty)
 * @link originally at https://codex.wordpress.org/Function_Reference/in_category#Testing_if_a_post_is_in_a_descendant_category
 */

if ( ! function_exists( 'wpdocs_post_is_in_a_subcategory' ) ) {
function wpdocs_post_is_in_a_subcategory( $categories, $_post = null ) {
    foreach ( (array) $categories as $category ) {
        // get_term_children() only accepts integer ID
        $subcats = get_term_children( (int) $category, 'category' );
        if ( $subcats && in_category( $subcats, $_post ) )
            return true;
    }
    return false;
  }
}
?>

    Use for checking if within a single cat:

    wpdocs_post_is_in_a_subcategory( 25 );

    Use for checking if within an array of parent categories, or any of their subcats:

    wpdocs_post_is_in_a_subcategory( array( 25, 28, 124, 297, 298, 299 ) );

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