API CMD_API_SHOW_USERS return Empty array

[feerdispzoo]

<?php

include '../protocol/httpsocket.php';

$sock = new HTTPSocket;

$sock->connect('localhost',2222);
$sock->set_login("admin","xxxxxxx");
$sock->set_method('GET');
$sock->query("/CMD_API_SHOW_USERS");

$result = $sock->fetch_parsed_body();

print_r($result);

?>

I dont know what is going on. Everytime I get only:
Array ( )