使用mysql查询获取多维数组作为结果

Question

I have a campaigns table which is related shop table based on shop_id, There are also a rules table which is related to campaigns table based on for_camp_id. I have to fetch the all the data from campaigns table based on shop_id with all the rules created for that specific campaign. I used join query as

return DB::table('campaigns')
    ->join('rules', 'campaigns.for_camp_id', '=', 'rules.for_camp_id')
    ->where('campaigns.for_shop_id',$shopId)
    ->get();

But it gives me record as a array of collection having each collection with single rules with campaign data. I want the result should be returned in proper formatting like a multidimensional array containing array for each campaign, and each campaign array containing created rules for it like

array(
    'campaign1'=array(
        'rule1'=>array(),
        'rule2'=array()
    ),
    'campaign2'=array(
        'rule1'=>array(),
        'rule2'=array()
    ),
)