just return the array, no need to assign it to anything. i.e.
return array('cashierId'=>$BillsCashierID ,
'CashierTotal'=>$CashierTotal ,
'CashierLastTotal'=>$CashierLastTotal );
or do
$cashier_data = array('cashierId'=>$BillsCashierID ,
'CashierTotal'=>$CashierTotal ,
'CashierLastTotal'=>$CashierLastTotal );
return $cashier_data;
then when you return it with $cd = GetCashierDetail(1);
you can access $cd['CashierTotal']