Passing php array as variables to javascript load url and back to php array?

I saw many examples related but I'm still confused. I'm using ajax (which I don't know much about) to get the results of a file updated every xxx seconds. It's working perfectly if I pass just one variable, but what is the best way if I need to pass an array from php through it?

Structure is simples:

show_results.php

<?php
include_once('modWhosonlineCustom.inc.php');
$document->addScript("http://code.jquery.com/jquery-latest.js");
$document->addScript("ajax.js");
$array_name = modWhosonlineCustom::getOnlineUserNames();//the array I need to pass to javascript variable
?>

<script>
var whosonline = '<?php echo "$array_name"; ?>';
</script>

<div id="results"></div>

Ajax code than would have more than one param to build in the url load:

  ajax.js

  $(document).ready(function() {
    $("#results").load("response.php?array_name[param1]&array_name[param2]");
  var refreshId = setInterval(function() {
  $("#results").load("response.php?array_name[param1]&array_name[param2]&randval="+ Math.random());
  }, 10000);
  $.ajaxSetup({ cache: false });
  });

And back to PHP response page, how could I use again the array params passed through url?

  response.php

  <?php
  $names = $_GET['array_name'];
  foreach ($names as $name) {
  //do something

Any suggestions is really appreciated, thanks!

EDIT

Thanks guys, I think I'm the right way now, but ramains the problem to pass this array through a url in the javascript. Or maybe I'm not getting it in the right way in the php end callback file. I'll show you what a modifyed:

   show_results.php

   ...
   <?php
   $names = modWhosonlineCustom::getOnlineUserNames();
   ?>

   <script>
   var whosonline = '<?php echo "json_encode($names)"; ?>';
   </script>


   ajax.js


   $(document).ready(function() {
   $("#atendentes").load("response.php?names=" + whosonline);
   var refreshId = setInterval(function() {
   $("#atendentes").load("response.php?names=" + whosonline + "&randval="+ Math.random());
   }, 10000);
   $.ajaxSetup({ cache: false });
   });


   response.php


   $users = $_GET['names'];
   $users = json_decode($users);
   echo "user: $users";

   $names = $users;
   foreach ($names as $name) {
   ...

Here in the other side I'm getting: Warning: Invalid argument supplied for foreach() in response.php on line 33, and the echo is empty

What is missing?