Having a for loop error ,not getting the correct output

This is the program i need the below output

http://ift.tt/1TKy5zg

But i am getting this output

http://ift.tt/1rTapju

But i am getting all the subcategories inside the category where is my problem i know its some where in the loop

<?php
namespace App\Model;
use Illuminate\Database\Eloquent\Model;
use Exception;
use Hash;
use DB;

class Rewards extends Model
{
    /**
     * The database table using by the model
     *
     * @var string
     */
    protected $primaryKey = 'id_category';

    public static function getrewardcategory()
    {
        $firstarray = array();
        $secondarray = array();
        $thirdarray = array();

        //Taking the top main categories - Bronze,silver 
        $mainrewards=\DB::table('product_for')->get();

        //Taking the rewards category
        $rewardcategory = DB::table('product_category')->where('parent_id','0')->where('mainparent','2')->get();

        foreach ($rewardcategory as $recat) 
        {
            //Taking the rewards sub category
            $rewardssubcategory=DB::table('product_category')->where('parent_id','>','0')
                                                             ->where('mainparent','2')
                                                             ->get();

            foreach ($rewardssubcategory as $resubcat) 
            {   
                    if($resubcat->parent_id ==$recat->id_category )
                    {                       
                        $rewardssubcategories = array('r_sub_categories_id' =>$resubcat->id_category,
                                                      'r_sub_categories_name' =>$resubcat->name,
                                                      'r_sub_categories_image' => "Sub cat Image URL"   
                                                      );
                        array_push($firstarray,$rewardssubcategories);
                    }

            }

        }
        foreach ($rewardcategory as $recat) 
        {                    
            $rewardscategories = array('r_categories_id' =>$recat->id_category,
                                       'r_categories_name' => $recat->name,
                                       'r_sub_categories' => $firstarray            
                                       );
            array_push($secondarray,$rewardscategories);
        }

        foreach ($mainrewards as $rewards) 
        {              
            $rewards = array('r_id' =>$rewards->id_product_for,
                         'r_name' => $rewards->product_for,
                         'r_image' => "image_url",
                         'r_categories'    => $secondarray
                        );
            array_push($thirdarray,$rewards);       
        }

    return $thirdarray;
    }
}

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