CodeIgniter中的递归函数失败

我正在使用递归函数转换树中的菜单。我从数据库中得到的数组是：

array ( 
  [0] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 1 
    [parent] => 0 
    [name] => Meter Reading 
    [link] => # ) 
  [1] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 2 
    [parent] => 0 
    [name] => Parameterization 
    [link] => # ) 
  [2] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 3 
    [parent] => 0 
    [name] => View Reports 
    [link] => # ) 
  [3] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 4 
    [parent] => 0 
    [name] => Management & Control 
    [link] => # ) 
  [4] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 5 
    [parent] => 1 
    [name] => Billing Data 
    [link] => # ) 
  [5] => stdClass Object ( 
    [nav_group_id] => 1 
    [entity_id] => 6 
    [parent] => 1 
    [name] => MDI Billing Data
    [link] => # )

我通过将上面提到的数组传递给以下函数来调用递归函数：

$this->parseAndPrintTree('0',$navigation_all);
//die();   (issue here)

现在，如果我在这个功能之后使用die();，它会显示正确的菜单，如果不使用die();，页面将无法加载，并给出以下错误：

内容编码错误您试图查看的页面无法显示，因为它使用了无效或不受支持的压缩形式。"

并且没有显示输出。这是我的递归函数：

function parseAndPrintTree($root, $tree) 
{
    $return = array();
    if(!is_null($tree) && count($tree) > 0) 
    {
        echo '<ul>';
        foreach($tree as $child => $parent) 
        {
            if($parent->parent == $root) 
            {                    
                unset($tree[$child]);
                echo '<li>'.$parent->name;
                $this->parseAndPrintTree($parent->entity_id, $tree);
                echo '</li>';
            }
        }
        echo '</ul>';
    }
}