AJAX request to PHP Database query returns no value

Hi,

I want to query my database using AJAX with JQUERY. This is the Javascript function I wrote to initiate the call:

var requestResponders = function(e) {
    e.preventDefault();
    getResponders(latitude, longitude, function(data) {
        console.log(data);
    });
}

And the AJAX request:

function getResponders(latitude, longitude, callback) {
    $.ajax({
        type: 'POST',
        url: '../searchResponders',
        data: {
            latitude: latitude,
            longitude: longitude
        },
        success: function(responders) {
            console.log(responders);
            callback(responders);
        },
        error: function(e) {
            console.log("Error");
        }
    })
};

Therefore I set in my routes file:

    Route::post('searchResponders', 'RespondersController@getAvailableResponders');

And the PHP to MYSQL Query:

    public function searchResponders($geoInformation) {
        $lat = $geoInformation['latitude'];
        $lng = $geoInformation['longitude'];
        $results = DB::select(DB::raw("SELECT id, (6371 * acos(cos(radians(:var1)) * cos(radians(last_lat)) * cos(radians(last_lng)-radians(:var2))+sin(radians(:var3))*sin(radians(last_lat)))) AS distance FROM responders HAVING distance < 2 ORDER BY distance LIMIT 0, 3"), array('var1' => $lat, 'var2' => $lng, 'var3' => $lat));
        echo json_encode($results);
    }

Now something strange happens. If I use POSTMAN to check the POST call, I receive the database output perfectly fine. So I can be sure already, that the SQL part and the routing works.

But when I check the AJAX call to the same function, it returns and empty return value. So usually I would think, this means that something is being returned before the PHP DB call finished. But this should be excluded by using the deferred object.

When I log the output in the console, I see that the code in the "done" section is being called, but the result return value is empty.

Why is that?