Вывод подкатегорий

Есть функция вывода категорий:

Class My_Categories_Widget extends WP_Widget_Categories {
	function widget( $args, $instance ) {
		static $first_dropdown = true;
		$title = apply_filters( 'widget_title', empty( $instance['title'] ) ? __( 'Categories' ) : $instance['title'], $instance, $this->id_base );
		echo $args['before_widget'];
		if ( $title ) {
			echo $args['before_title'] . $title . $args['after_title'];
		}

		echo '<ul class="left-nav nav nav-pills nav-stacked">';
		$args = array(
			'orderby' => 'slug',
			'parent' => 0,
			'show_count'   => 1
		);
		$categories = get_categories( $args );
		global $wp;
		$current_url = home_url(add_query_arg(array(),$wp->request));
		foreach ( $categories as $category ) {
			$var2 = get_category_link( $category->term_id );
			$var2 = substr($var2,0,strlen($var2)-1); 
			if(strcasecmp($current_url, $var2) == 0)
				echo '<li class="active"><a href="' . get_category_link( $category->term_id ) . '" rel="bookmark"><i class="ss-icon"
			aria-hidden="true">' . $category->name . '</i>' . '<span>' . $category->count . '</span></a></li>';
			else
			echo '<li><a href="' . get_category_link( $category->term_id ) . '" rel="bookmark"><i class="ss-icon"
			aria-hidden="true">' . $category->name . '</i>' . '<span>' . $category->count . '</span></a></li>';
		}
		echo '</ul>';
		echo $args['after_widget'];
	}
}

Нужно вывести подкатегории. Помогите вывести кому не трудно