drop_down.php

<form name="_token" action="{{ route('bookings.toursDropDown', $tour->id) }}" id="tour-dropdown" method="get" value="<?php echo csrf_token(); ?>">
                    {!! csrf_field() !!}
                        <select id="tour">                      
                            <option value="">All</option>
                            @foreach ($tours as $tour)
                                <option value="{!! $tour->id !!}">{!! $tour->name !!}</option>
                            @endforeach
                        </select>
                    </form>
                </td>

<script>

            function dataFilter(id){
                $(id).on('change', function(e){

                    var variable = e.target.value;

                    $(id + '-dropdown').submit();

                });
            };

            dataFilter('#tour');

            dataFilter('#category');

            dataFilter('#region');

            dataFilter('#dates');

</script>