Query builder with 4 tables [duplicate] - development

Query builder with 4 tables [duplicate]

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This is my query builder function :

public function MonthSoldGDV($dev,$year){

            $monthlyGDV = DB::table('pams_unit')
            ->join('pams_phase','pams_unit.phase_id','pams_phase.phase_id')
            ->join('pams_project','pams_phase.project_id','pams_project.project_id')
            ->join('pams_developer','pams_project.dev_id ','pams_developer.id')
            ->select('pams_developer.developer_name')
            ->selectRaw('year(pams_unit.sold_date) as year')
            ->selectRaw('month(pams_unit.sold_date) as month')
            ->selectRaw('sum(pams_unit.sold_price) as gdv')
            ->where('pams_developer.developer_name','$dev')
            ->whereRaw('year(sold_date) = $year')
            ->groupBy('month')
            ->get();

            return $monthlyGDV;

        }

But it show an error Column not found: 1054 Unknown column '$year' in 'where clause'

Can someone help me to figure out my problem ?

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