arrays.php

<?php

// prepare options
$a = array(
      'top 1' => array(
          'sub 1' => 100,
          'sub 2' => array('sub sub 1' => 101, 'sub sub 2' => 102),
      ),
      'top 2' => 103
     );

echo json_encode($a);
          

show.js

$.getJSON('ajax/arrays.php', function(data) {
    $('input[name=demo]').optionTree(data);
});