in_category( int|string|int[]|string[] $category, int|object $post = null )
Checks if the current post is within any of the given categories.
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.
Parameters
- $category
-  (int|string|int[]|string[]) (Required) Category ID, name, slug, or array of such to check against. 
- $post
-  (int|object) (Optional) Post to check instead of the current post. Default value: null 
Return
(bool) True if the current post is in any of the given categories.
Source
File: wp-includes/category-template.php
function in_category( $category, $post = null ) {
	if ( empty( $category ) ) {
		return false;
	}
	return has_category( $category, $post );
}  Changelog
| Version | Description | 
|---|---|
| 2.7.0 | The $postparameter was added. | 
| 1.2.0 | Introduced. | 
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Licensed under the GNU GPLv2+ License.
    https://developer.wordpress.org/reference/functions/in_category