(Laravel) สอบถามเรื่องการส่งค่า ajax แบบ post หน่อยครับ

<?php

Route::group(['middleware' => ['web']], function () {
            // Auth Route...
            Route::group(['middleware' => 'auth'], function () {

                // Ajax Route...
                Route::post('/ajax/cabinet', [
                    'before' => 'csrf',
                    'uses' => 'AjaxController@postCabinet'
                ]);
            });
});

        <div class="box-body">
            <div class="row">
                <div class="col-md-6">
                    {!! Form::open(['url' => '/', 'role' => 'form']) !!}
                    <div class="row">
                        <div class="col-md-5">
                            <div class="form-group">
                                {!! Form::label('cabinet', 'คณะรัฐมนตรี') !!}
                                {!! Form::select('cabinet',  $cabinets->lists('name', 'id'), 
                                    $cabinets->first(function($key, $value) { return $value['default'] == true; })->id, 
                                    ['class' => 'form-control']) !!}
                            </div>
                        </div>
                        <div class="col-md-5">
                            <div class="form-group">
                                {!! Form::label('budget_year', 'ปีงบประมาณ') !!}
                                {!! Form::select('budget_year', $budget_years->lists('name', 'id'),
                                    $budget_years->max('budget_year_id'), 
                                    ['class' => 'form-control']) !!}
                            </div>
                        </div>
                        <div class="col-md-2 bottom-align-text">
                            <div class="form-group">
                                {!! Form::submit('ตกลง', ['class' => 'form-control btn btn-primary']) !!}
                            </div>
                        </div>
                    </div>
                    {!! Form::close() !!}
                </div>
                <!-- /.col -->

                <div class="col-md-6">
                    <div class="pad">
                        <!-- Map will be created here -->
                        <div id="world-map-markers" style="height: 325px;"></div>
                    </div>
                </div>
                <!-- /.col -->
            </div>
            <!-- /.row -->

$('#cabinet').change(function () {
    $.ajax({
        url: 'ajax/cabinet',
        type: "post",
        data: {
            'cabinet': $('#cabinet').find(":selected").val(),
            '_token': $("input[name='_token']").val()
        },
        success: function (budgetYears) {
            var options = '';

            $.each(budgetYears, function (i, budgetYear) {
                options += '<option value="' + budgetYear.id + '"' + ((budgetYears.length == i + 1) ? ' selected="selected"' : '') + '>' + budgetYear.name + '</option>'
            });

            $('#budget_year').html(options);
        }
    });
});

<?php

namespace App\Http\Controllers\Webapp;

use Illuminate\Http\Request;

use App\Http\Requests;
use App\Http\Controllers\Controller;
use Input;
use App\Cabinet;

class AjaxController extends Controller
{
    public function postCabinet() {
        $cabinet_id = Input::get('cabinet');

        $budget_years = Cabinet::where('id', $cabinet_id)
            ->first()
            ->budget_years()
            ->orderBy('id', 'asc')
            ->get();

        return $budget_years;
    }
}