I'm trying to sort with Jquery UI in Laravel and it's giving me fits.

Here is my controller:

public function postSortSongs(Request $request)
{
    $i = 1;

    foreach ($request->list_order as $value) {
        $i++;
        Songs::where('id', '=', $value)->update(['sort_no' => $i]);
    }
}

Here's my Javascript:

<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.3/jquery-ui.min.js"></script>
<script>
    var getXsrfToken = function () {
        var cookies = document.cookie.split(';');
        var token = '';

        for (var i = 0; i < cookies.length; i++) {
            var cookie = cookies[i].split('=');
            if (cookie[0] == 'XSRF-TOKEN') {
                token = decodeURIComponent(cookie[1]);
            }
        }

        return token;
    };
    $.ajaxSetup({
        headers: {
            'X-XSRF-TOKEN': getXsrfToken()
        }
    });

    $(document).ready(function(){
	    $('#sortable').sortable({
	        axis: 'y',
	        opacity: 0.7,
	        update: function(event, ui) {
	            var data = $(this).sortable('serialize');

	            $.ajax({
	                url: '{{ route('show_sort_songs_save') }}',
	                type: 'POST',
	                data: data
	            });
	        }
	    });
	});
</script>

Here is my view:

        <ul id="sortable">
            
            @foreach($songs as $song)
	            <li id="item-{{ $song->id }}">{{ $song->title_of_song->song_title }}</li>
            @endforeach
            
        </ul>

And I'm getting an internal 500 error:

send	@	jquery.js:26
ajax	@	jquery.js:25
update	@	main:148
_trigger	@	jquery-ui.min.js:6
_trigger	@	jquery-ui.min.js:12
(anonymous)	@	jquery-ui.min.js:6
(anonymous)	@	jquery-ui.min.js:12
_clear	@	jquery-ui.min.js:12
(anonymous)	@	jquery-ui.min.js:6
_mouseStop	@	jquery-ui.min.js:12
(anonymous)	@	jquery-ui.min.js:6
_mouseUp	@	jquery-ui.min.js:6
(anonymous)	@	jquery-ui.min.js:6
n._mouseCapture._mouseDistanceMet._mouseDelayMet._mouseUpDelegate	@	jquery-ui.min.js:6
dispatch	@	jquery.js:25
q.handle	@	jquery.js:24

Can anyone help me? I've looked all over the web and can't find a solution that can help me.