PHP REST API query returning empty body

I cannot get my PHP Rest API to work, it is just returning empty body with a successful HTTP request(200).

When I just echo something out it returns it fine. I am using Slim (PHP micro framework), MySQL,apache. Database table is created in phpmyadmin.

index.php

<?php

use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;

require '../vendor/autoload.php';
require '../src/config/db.php';

$app = new \Slim\App;
$app->get('/hello/{name}', function (Request $request, Response $response) {
    $name = $request->getAttribute('name');
    $response->getBody()->write("Hello, $name");

    return $response;
});

// Customer Routes
require '../src/routes/dates.php';

$app->run();

db.php it also contains dbhost, dbuser, dbpass and dbname variables above

<?php
class db
{
    // Properties
    var $dbhost = 'localhost';
    var $dbuser = 'root';
    var $dbpass = 'parool1';
    var $dbname = 'slimapp';

    // Connect
    public function connect()
    {
        $mysql_connect_str = "mysql:host=$this->dbhost;dbname=$this->dbname";
        $dbConnection = new PDO($mysql_connect_str, $this->dbuser, $this->dbpass);
        $dbConnection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $dbConnection;
    }
}

dates.php

<?php

use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;

$app = new \Slim\App;

// Get All Calendar Dates
$app->get('/api/date', function (Request $request, Response $response) {
    $sql = "SELECT * FROM `calendardates`";

    try {
        // Get DB Object
        $db = new db();
        // Connect
        $db = $db->connect();

        $stmt = $db->query($sql);
        $dates = $stmt->fetchAll(PDO::FETCH_OBJ);
        $db = null;
        echo json_encode($dates);
    } catch (PDOException $e) {
        echo '{"error": {"text": ' . $e->getMessage() . '}';
    }
});

Solution:

Change collation of database table to utf8 (if you want to use charcaters like "ö, ä, ü" in your database table).

I changed

$dbConnection = new PDO($mysql_connect_str, $this->dbuser, $this->dbpass);

to

$dbConnection = new PDO($mysql_connect_str, $this->dbuser, $this->dbpass, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

to fix the problem.