post_link_category filter-hook . WP 3.5.0

Filters the category that gets used in the %category% permalink token.

Usage

add_filter( 'post_link_category', 'filter_function_name_500', 10, 3 );
function filter_function_name_500( $cat, $cats, $post ){
	// filter...

	return $cat;
}

$cat(WP_Term)

The category to use in the permalink.

$cats(array)

Array of all categories (WP_Term objects) associated with the post.

$post(WP_Post)

The post in question.

Where the hook is called

$category_object = apply_filters( 'post_link_category', $cats[0], $cats, $post );

Where the hook is used (in WP core)