WordPress loop through posts with hierarchy

Submenu.php

<?php
	private function get_all_posts( $post_id, $type = 'page' ) {

		//* $posts is an array
		$posts = get_posts( array(
			'post_type' => $type,
			'post_parent' => $post_id,
			'nopaging' => true,
			'orderby' => 'menu_order',
			'hierarchical' => true,
			'suppress_filters' => false
		) );

		foreach ( $posts as $key => $post ) {

			$posts[$key] = (array) $post;
			$posts[$key]['subnav'] = $this->get_all_posts( $post->ID );

		}

		return $posts;
	}