function post_comment(id,date,name,comment,challenge,response) {
    var url = 'includes/functions/ajax_handler.php?action=post_comment&id=' + id + '&date=' + date + '&name=' + name + '&comment=' + comment + '&challenge=' + challenge + '&response=' + response;
    
    new Ajax.Request(url, {
        evalJSON: true,
        onSuccess: function(response) {
            var new_comment = response.responseJSON;
            if(new_comment instanceof Array) {
                render_comment(new_comment[2],new_comment[3],new_comment[4]);
            } else {
                // there was an error
                alert(response.responseText);
            }
        }
    });
}