ลองทำโจทย์ พี่เล็ก

Route::get('/lexsoft', function () {

    $datas = \App\Lexsoft::oldest('datefrom')->get();
    $arrResult = [];

    foreach ($datas as $key => $data) {

        $dateFrom = new DateTime($data->datefrom);
        $datetTo = new DateTime($data->dateto);
        $interval = $dateFrom->diff($datetTo);
        $days = $interval->format('%a');

           $arrResult[] = [
            "id" => $data->id,
            "date_from" => $data->datefrom,
            "date_to" => $data->dateto,
            "diff_day" => $days + 1
        ];

        for ($i = $dateFrom; $i <= $datetTo; $i->modify('+1 day')) {

            $arrResult[$key]['result'][] = $i->format("Y-m-d");

        } //end for
    } //end foreach

    dd($arrResult);

});