populating a table in a jquery dialog with json results - php

Question

When the user clicks on the button to view the comments, a jquery dialog opens with the list of comments. I can't quite figure out how to get the results to populate the table on success. I found some posts that said to use the .append (in my code) but it's not working for me and I'm not sure what I am missing.
PHP Code:
if(isset($_GET['parcel_id'])) {
$db = new ezSQL_mysql(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
$comments = $db->get_results("SELECT * FROM comments where parcel_id=" . $_GET['parcel_id']);
if($comments != null) echo json_encode($comments);
/*foreach ($comments as $comment){
echo "<table><tr><td>" . $comment->date_created . "</td><td style=\"text-align:right;\">" . $comment->user_id . "</td></tr>";
echo "<tr><td colspan=\"2\">" . $comment->comment . "</td></tr></table>";
}*/
}
jQuery Code:
$('#ViewComments').click(function() {
$("#InsertComment").focus();
//view/add comments dialog
$( "#CommentsDialog" ).dialog({
height:320,
width: 500,
modal:true,
closeOnEscape:true,
buttons: [ { text: "Close", click: function() { $(this).dialog( "close" ); } } ]
});
var parcel_id = $('#ParcelId').val(parcel_id);
$.ajax({
url: "classes/get-comments.php?parcel_id=" + parcel_id,
type: "GET",
data: { parcel_id : parcel_id },
error: function(SMLHttpRequest, textStatus, errorThrown){
alert("An error has occurred making the request: " + errorThrown);
},
success: function(comments){
//do stuff here on success
//<div id="Comments"><table id="CommentResults">
var tr;
for(var i=0; i < comments.length; i++){
tr = $('<tr/>');
tr.append("<td>" + json[i].date_create + "</td>");
tr.append("<td style=\"text-align:right;\">" + json[i].user_id + "</td></tr>");
tr.append("<tr><td colspan=\"2\">" + json[i].comment + "</td>");
$('#CommentResults').append(tr);
}
}
});
});//end view comments click function
HTML:
<div id="CommentsDialog" title="Comments">
<div style="width:98%;height:75%; margin-bottom:5px; background-color: #fff; padding:5px;" id="Comments" name="Comments">
<table id="CommentResults" name="CommentResults"></table>
</div>
<input type="text" style="width:65%;margin-top:5px;" id="InsertComment" /> <input type="button" id="AddComment" value="Add Comment" class="floatRight" />
</form>
</div>