semoga solve

<?php
$array = null;
//========ini udah ok.. tp hrs ada 1 perbaikan ptg disini
    foreach ($row->result_object as $row) {
        if($row->parent == ""){
            $menu_parent[0][$row->id] = $row;
        }else{
            $menu_parent[$row->parent][] = $row;
        }
    }
//===========disambung pake coding gw
class menu {
    //put your code here
    private $menu;
    function __CONSTRUCT(){
        $menu = array(
            'top' => array(
                array(6, 'one menu'),
                array(1, 'multi menu')
            )
        );

        $menu['sub'] = array(
            '1' => array(
                array(2, 'one menu'),
                array(11, 'multi menu')
            )
        );
        $menu['sub'][11]=array(
                array(3, 'one menu'),
                array(4, 'multi menu')
            );
        $this->menu=$menu;
    }

    function update($menu){
     $this->menu=$menu;
     }

    function get(){
        return $this->menu;
    }

    function run(){

        return $this->get_parent();
    }
    //=============FOKUS pada ini saja
    function get_parent(){//get_list

        $data= $this->menu[0];//or parent

        $raw=array();
        foreach($data as $row){
            $tmp = array('id'=>$row[0], 'text'=>$row[1]); //mending langsung dibuat gini walau dari query udah melakukannya
            $have_child=$this->have_child($row[0]);
            if($have_child){
                $tmp['child']=$this->get_child($row[0]);
            }
            $raw[]=$tmp;
        }
        return $raw;
    }

    function have_child($id){
        $child=$this->menu['sub'];
        return isset($child[$id])?TRUE:FALSE;
    }

    function get_child($id){
        $data = $this->menu[$id];//or child
        //$data=$data_child[$id]; //asumsikan kamu dapatkan dari query where parent=xxx
        $raw=array();
        foreach($data as $row){
            $tmp = array('id'=>$row[0], 'text'=>$row[1]); //mending langsung dibuat gini walau dari query udah melakukannya
            $have_child=$this->have_child($row[0]);
            if($have_child){
                $tmp['child']=$this->get_child($row[0]);
            }
            $raw[]=$tmp;
        }
        return $raw;
    }
}

$menu = new menu($menu_parent);

$ar = $menu->run();

echo '<pre>'.print_r($ar,1).  json_encode($ar);