Walker_Category example

function walk_category_tree( ...$args ) {
    // The user's options are the third parameter.     if ( empty( $args[2]['walker'] ) || ! ( $args[2]['walker'] instanceof Walker ) ) {
        $walker = new Walker_Category();
    } else {
        /** * @var Walker $walker */
        $walker = $args[2]['walker'];
    }
    return $walker->walk( ...$args );
}

/** * Retrieves HTML dropdown (select) content for category list. * * @since 2.1.0 * @since 5.3.0 Formalized the existing `...$args` parameter by adding it * to the function signature. * * @uses Walker_CategoryDropdown to create HTML dropdown content. * @see Walker::walk() for parameters and return description. * * @param mixed ...$args Elements array, maximum hierarchical depth and optional additional arguments. * @return string */