Joomla模块和Jquery

I have a module with three drop-downs, in one class, depending on each other. I have the first drop-down that loads the data from MySQL. I would like that the second one loads the data depending on the first selected value. Currently I have this code:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
function curPageURL() {
    var pathname = window.location.pathname;
    return pathname;
}

$(document).ready(function(){
    $('#art1').change(function(){
       var $height = $('#art2') ;
       $height.find('option:not([value=default])').remove();
       $.getJSON(curPageURL(), {height:$(this).val()}, function(heights){
          $.each(heights, function(index, height){
              $height.append('<option value="'+height[0]+'">'+height[1]+'</option>');
          });
       });
    });
});
</script>

This goes in the default.php and if height is set it executes and MySQL statement from another class which works fine and then encodes it to json. But firebug is giving me this error

ERROR: JSON.parse: unexpected character

and as I'm looking in the data it is returning a whole html code.

I solved this by connecting my module with the component following this tutorial http://forum.joomla.org/viewtopic.php?p=2424982