$app->get('/filname/getallusers', function (Request $request, Response $response)
{
$db = $this->get(PDO::class);
$sql = "SELECT username FROM talbename";
$exec_sql = $db->prepare($sql);
$exec_sql->execute();
$data = $exec_sql->fetchAll(PDO::FETCH_ASSOC);
$data_encode = json_encode($data);
$response->getBody()->write($data_encode);
return $response->withHeader('Content-Type', 'application/json');
});