不要提醒AJAX

I'm trying to get result and alert it if the solicitude was successful or not on the PHP file, it worked (because changed the results) but the AJAX didn't show alerts (No error and no "true")

js:

function addentrys() {
    var nwentry =  {};
    el = document.getElementById('addname').value;
    eldmn = document.getElementById('adddomain').value;
    nwentry.name = el;
    nwentry.domain = eldmn;

    $.ajax({
        type: 'POST',
        url: 'api/domain',
        dataType: 'json',
        data: nwentry
    }).done(function(data) {
        alert(data);
    });
}

php:

    $app->post('/domain', function () {
    $jsonContents = file_get_contents('data/data.json');
    $name = $_POST['name'];
    $domain = $_POST['domain'];
    $data = json_decode($jsonContents, true);
    $last_item = end($data);
    $last_item_id = $last_item['id'];
    $data[] = array(
        'name' => $name,
        'domain' => $domain,
        'id' => $last_item_id+1
    );


    $json = json_encode($data);
    file_put_contents('data/data.json', $json);
    return true;
});