Как вывести подкатегории?

public static function getCategoriesList(){ 
		$db = Db::getConnection(); 
		$categoryList = array(); 
 
		$result = $db->query('SELECT id, name, sort_order, status, parent_id FROM category '. 'ORDER BY sort_order ASC'); 
 
		$i = 0; 
		while ($row = $result->fetch()) { 
			$categoryList[$i]['id'] = $row['id']; 
			$categoryList[$i]['name'] = $row['name']; 
			$categoryList[$i]['sort_order'] = $row['sort_order']; 
			$categoryList[$i]['status'] = $row['status']; 
      $categoryList[$i]['parent_id'] = $row['parent_id']; 
			$i++; 
		} 
 
		return $categoryList; 
	} 
 
  public static function getSubCategoriesList(){ 
    $db = Db::getConnection(); 
    $subCategoryList = array(); 
 
    $result = $db->query('SELECT * FROM `category` WHERE `parent_id` =' . $id); 
 
    $i = 0; 
    while ($row = $result->fetch()) { 
      $subCategoryList[$i]['id'] = $row['id']; 
      $subCategoryList[$i]['name'] = $row['name']; 
      $i++; 
    } 
 
    return $subCategoryList; 
  }

class SiteController 
{ 
 
  public function actionIndex() 
  { 
    $categories = array(); 
    $categories = Category::getCategoriesList(); 
 
 		$subCategories = array(); 
    $subCategories = Category::getSubCategoriesList(); 
 
    $latestProducts = array(); 
    $latestProducts = Product::getLatestProducts(8); 
     
    require_once(ROOT . '/views/site/index.php'); 
 
    return true; 
  } 
}

<ul> 
	<?php foreach ($categories as $categoryItem): ?> 
		<li> 
			<p class="aside__title"><?php echo $categoryItem['name'];?></p> 
			<?php echo $categoryItem['id'];?> 
			<div class="aside__plus"> 
				<span></span><span></span> 
			</div> 
			<ul> 
				<?php foreach ($subCategories as $categorySubItem => $id): ?> 
					<li> 
						<a href="/category/<?php echo $categorySubItem['id'];?>"> 
							<?php echo $categorySubItem['name'];?> 
						</a> 
					</li> 
				<?php endforeach; ?> 
			</ul> 
		</li> 
	<?php endforeach; ?> 
</ul>