WordPress at a glance
filter is not described

get_categories_taxonomy filter-hook . WP 2.7.0

Filters the taxonomy used to retrieve terms when calling get_categories().

Usage

add_filter( 'get_categories_taxonomy', 'filter_function_name_8169', 10, 2 );
function filter_function_name_8169( $taxonomy, $args ){
	// filter...

	return $taxonomy;
}
$taxonomy(string)
Taxonomy to retrieve terms from.
$args(array)
An array of arguments. See get_terms().

Where the hook is called

get_categories()
wp-includes/category.php 40
$taxonomy = apply_filters( 'get_categories_taxonomy', $taxonomy, $args );

Where the hook is used (in WP core)

Does not used.