How to create a new array by grouping values for same id

I have a table where it has amount,director_id. I am trying create an array by adding amount of same Director id so that i can pass it to blade to create a table. but it ignoring the last values for each id.

Bellow is my code, but its gives wrong out put

$expense_details = DB::table('receipts')
            ->join('directors', 'directors.id', '=', 'receipts.director_id')
           ->join('account_type', 'account_type.id', '=', 'receipts.type')
            ->join('expense_type', 'expense_type.id', '=', 'receipts.exp_earn_type')

            ->select('receipts.*', 'directors.name as directors_name','account_type.name as account_name', 'expense_type.name as exp_name')
            ->get();

    dd($expense_details);



       $investor_total_by_id=[];

        $exp_amount=0;
      foreach ($expense_details as $exp){


          if (isset($investor_total_by_id[$exp->director_id])) {
              $exp_amount= $exp_amount + $exp->amount;
              $investor_total_by_id[$exp->director_id] = $exp_amount;

          }else {
              $investor_total_by_id[$exp->director_id] = $exp->amount;
          } 



       }

       //dd($investor_total_by_id);
        return view('Accounts/Investment/add')
             ->with('expense_details',$expense_details)
            ->with(' investor_total_by_id',  $investor_total_by_id)

        ;

the Table Array is like this I am trying to group/add amount for each director_id

Main table

Collection {#522 ▼
  #items: array:6 [▼
    0 => {#526 ▼
      +"id": 24
      +"type": 2
      +"exp_earn_type": 11
      +"sale_id": 0
      +"receipt_date": "2019-04-29 00:00:00"
      +"amount": 100.0
      +"description": "aesf"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 1
      +"emp_id": 0
      +"created_at": "2019-04-18 07:26:10"
      +"updated_at": "2019-04-18 07:26:10"
      +"directors_name": "Siam"
      +"account_name": "Expenses"
      +"exp_name": "Travel Expense"
    }
    1 => {#530 ▼
      +"id": 25
      +"type": 2
      +"exp_earn_type": 9
      +"sale_id": 0
      +"receipt_date": "2019-04-16 00:00:00"
      +"amount": 1000.0
      +"description": "ff"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 1
      +"emp_id": 0
      +"created_at": "2019-04-18 15:58:11"
      +"updated_at": "2019-04-18 15:58:11"
      +"directors_name": "Siam"
      +"account_name": "Expenses"
      +"exp_name": "GpsTrackingDevices"
    }
    2 => {#528 ▼
      +"id": 26
      +"type": 2
      +"exp_earn_type": 18
      +"sale_id": 0
      +"receipt_date": "2019-04-17 00:00:00"
      +"amount": 1000.0
      +"description": "ttt"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 1
      +"emp_id": 0
      +"created_at": "2019-04-18 17:45:54"
      +"updated_at": "2019-04-18 17:45:54"
      +"directors_name": "Siam"
      +"account_name": "Expenses"
      +"exp_name": "Computer – Hardware"
    }
    3 => {#527 ▼
      +"id": 27
      +"type": 2
      +"exp_earn_type": 13
      +"sale_id": 0
      +"receipt_date": "2019-04-15 00:00:00"
      +"amount": 5000.0
      +"description": "gg"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 1
      +"emp_id": 3
      +"created_at": "2019-04-18 21:01:37"
      +"updated_at": "2019-04-18 17:46:59"
      +"directors_name": "Siam"
      +"account_name": "Expenses"
      +"exp_name": "Payroll – Salary & Wages"
    }
    4 => {#525 ▼
      +"id": 28
      +"type": 2
      +"exp_earn_type": 17
      +"sale_id": 0
      +"receipt_date": "2019-04-15 00:00:00"
      +"amount": 222.0
      +"description": "ddd"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 2
      +"emp_id": 0
      +"created_at": "2019-04-18 19:22:36"
      +"updated_at": "2019-04-18 19:22:36"
      +"directors_name": "Riad"
      +"account_name": "Expenses"
      +"exp_name": "Rent Expense"
    }
    5 => {#529 ▼
      +"id": 29
      +"type": 2
      +"exp_earn_type": 16
      +"sale_id": 0
      +"receipt_date": "2019-04-11 00:00:00"
      +"amount": 222.0
      +"description": "22"
      +"device_imei": "0"
      +"operator_id": 2
      +"director_id": 2
      +"emp_id": 0
      +"created_at": "2019-04-18 19:22:54"
      +"updated_at": "2019-04-18 19:22:54"
      +"directors_name": "Riad"
      +"account_name": "Expenses"
      +"exp_name": "Office Supplies"
    }
  ]
}

I am getting this result

array:2 [▼
  1 => 7000.0
  2 => 7222.0
]

but it should be

array:2 [▼
  1 => 7100.0
  2 => 444.0
]

via Chebli Mohamed