Laravel 5.0 Join Sub Query With Request Paramters

Question

I'm trying to create a very complex query, I've simplified it as much as possible (2 select statements, are concatenated to the main query), the code below, works only If there are no "date" parameters sent in the request, When parameters sent, I got an error "SQLSTATE[HY000]: General error: 2031"

I think the problem is in toSql() method, but I don't know what else could I use to solve that?

Update: I need to keep leftJoin method so I can't use mergeBindings method

    // 1st select statement
    $earnQuery = DB::Table('san_charity_point_earn')->select('charity_id','earn_date',DB::raw('count(user_id) as users,sum(points) as earn_points,count(transaction_id) as earn_trans'))
    ->where(function($q) use($request){
        // filter paramters
        if($request->has("from")){
            $q->where("earn_date",">=",$request->from);
        }

        if($request->has("to")){
           $q->where("earn_date","<=",$request->to);
        }
    })
    ->groupBy('charity_id')
    ->toSql();


    // 2nd select statement
    $redeemQuery = DB::Table('san_charity_point_redeem')->select('charity_id','redeem_date',DB::raw('sum(points) as redeem_points,count(transaction_id) as redeem_trans'))
    ->where(function($q) use($request){
        // filter paramters
        if($request->has("from")){
            $q->where("redeem_date",">=",$request->from);
        }

        if($request->has("to")){
           $q->where("redeem_date","<=",$request->to);
        }
    })
    ->groupBy('charity_id')
    ->toSql();


  //full Query  
  $charities = DB::table('san_charity')->select('san_charity.charity_id','title_ar','title_en',DB::raw('
        COALESCE(users,0) as users, 
        COALESCE((earn_trans+redeem_trans),0) as transactions, 
        COALESCE(earn_points,0) as earn_points,
        COALESCE(redeem_points,0) as redeem_points'))
        ->leftJoin(DB::raw('('.$earnQuery.') earn'),function($join){
            $join->on('earn.charity_id','=','san_charity.charity_id');
        })
        ->leftJoin(DB::raw('('.$redeemQuery.') redeem'),function($join){
            $join->on('redeem.charity_id','=','san_charity.charity_id');
        })
        ->get();