ik heb de referentie nu toch gevonden maar hoe op te lossen ?

function in_category( $category ) { // Check if the current post is in the given category
global $post, $blog_id;

$categories = get_object_term_cache($post->ID, ‘category’);
if ( false === $categories )
$categories = wp_get_object_terms($post->ID, ‘category’);
if(array_key_exists($category, $categories))
return true;
else
return false;
}