WHERE IN array binding in DB::raw laravel 5.4

$arr = [1,2,3];
$result = DB::table('test1')->whereIn('id', $arr)->get();
dd($result);

$arr = [1,2,3];
$arr = join(",",$arr);
$result =  DB::select(DB::raw("SELECT * FROM test1 WHERE id IN (".$arr.")"));
dd($result);

 $arr = [1,2];
 $arr = join(",",$arr);
 $result =  DB::select(DB::raw("SELECT * FROM test1 WHERE id IN (?,?)"),$arr);
 dd($result);

$arr = [1,2,3];
$placeholders = implode(",", array_fill(0, count($arr), '?'));

DB::select("select * from test1 WHERE id IN ($placeholders)", $arr);

DB::table("test1")->whereIn('id', $arr)->get();

$q= TestModel::where('id',$arr)->get();

$array = [2,5,9,7,5];
$arrPos = [];
$arrBind = [];
foreach ($array as $pos => $id) {
    $arrPos[] = ":id_{$pos}";
    $arrBind["id_{$pos}"] = $id;
}

$sql = 
"  SELECT * FROM test1 WHERE id IN (".implode(', ', $arrPos).") ";
$rs = DB::select($sql, $arrBind);