Problem with WP_User_Query

I have updated my WordPress to the new version 4.0.1 and I got some problems. Before I had an old version, the 3.5.1 and everything was ok with my code. Pardon me for my bad english, I try to explain it.

I have this code:

$user_query = new WP_User_Query(array('ID'));
$users = (array) $user_query;

...

<select name="UsersZone" class="" style="width: 100%" onChange="setZoneUser(this.value);">

<option value="false">--Select A User--</option>

<?php

foreach($users["results"] as $user) {

?>

<option value="<?php echo $user->ID?>"><?php echo $user->display_name;?></option>

<?php

}

?>

</select>

So, with this code I should have a list of my Users. But I receive this error:

Warning: Invalid argument supplied for foreach() in /web/htdocs/www.mywebsite.com/home/... on line xxx

where xxx is the line

foreach($users["results"] as $user)

I have tried to use var_dump($users) and I got this:

array(8) {
  ["query_vars"]=>
  array(17) {

...

  }
  ["WP_User_Queryresults"]=>
  array(1) {
    [0]=>
    object(WP_User)#4246 (7) {
      ["data"]=>
      object(stdClass)#4244 (10) {
        ["ID"]=>
        string(1) "1"
        ["user_login"]=>
        string(5) "Admin"
        ["user_pass"]=>
        string(34) "xxx"
        ["user_nicename"]=>
        string(5) "admin"
        ["user_email"]=>
        string(26) "[email protected]"
        ["user_url"]=>
        string(0) ""
        ["user_registered"]=>
        string(19) "2014-11-26 18:55:12"
        ["user_activation_key"]=>
        string(0) ""
        ["user_status"]=>
        string(1) "0"
        ["display_name"]=>
        string(5) "Admin"
      }
      ["ID"]=>
      int(1)
      ["caps"]=>
      array(1) {
        ["administrator"]=>
        bool(true)
      }
      ["cap_key"]=>
      string(15) "wp_capabilities"
      ["roles"]=>
      array(1) {
        [0]=>
        string(13) "administrator"
      }
      ["allcaps"]=>
      array(63) {

...
  }
  ["filter"]=>
  NULL
    }
  }
  ["WP_User_Querytotal_users"]=>
  string(1) "1"
  ["query_fields"]=>
  string(30) "SQL_CALC_FOUND_ROWS wp_users.*"
  ["query_from"]=>
  string(13) "FROM wp_users"
  ["query_where"]=>
  string(9) "WHERE 1=1"
  ["query_orderby"]=>
  string(23) "ORDER BY user_login ASC"
  ["query_limit"]=>
  NULL
}

So the problem is in the field “WP_User_Queryresults” instead of “results”.

How can I solve this problem? Thank you.