2 Ajax responses from json_encode

[ebolt007]

So I have a script I'm working on that pulls multiple comments from a database, then puts it in a jquery piece that pulls the data from the arrays I created in my MYSQL Select.

function get_posts($start = 0, $number_of_posts = 5) {
$posts = array();
$comments = array();
$query = "
                    
                    SELECT PostID
                    FROM Users_WallPosts
                    
                    WHERE Users_WallPosts.UserID = '$user_ID'
 
                    ORDER BY DateAdded DESC LIMIT $start,$number_of_posts";
                		$result = mysql_query($query);
                		while($row = mysql_fetch_assoc($result)) {
                			$posts[] = $row;
 
                			$postsmain = $row['PostID'];
                			
                    $sql2 = "
                    SELECT Users_WallComments.Comment FROM Users_WallComments
                    LEFT JOIN Users_WallPosts 
                    ON Users_WallPosts.PostID = Users_WallComments.PostID 
                    where Users_WallPosts.PostID = '$postsmain'";
                    $result2 = mysql_query($sql2);
                		while($comments_row = mysql_fetch_assoc($result2)) {
                    $comments[] = $comments_row; 
                    }
 
 
		}
    json_encode($comments);
return json_encode($posts);
	}

Now I want it to pull those comments and posts in, I can get it to pull in one or the other, but I can't get the Posts to pull in, then the comments to pull in below that, basically like facebook. But I have this settup to only display so many comments then when you click the show more it loads more below the 5 so it doesn't load everything at the same time. I simplified my sql above, but the SQL's work fine, I'm good with PHP and sql, it's AJAX that I'm new too and confused with he below code. I'm guessing I need to json_encodes, and then use those, but how do I break these apart and use 2 json_encodes for my arrays above?

<script type="text/javascript">
		//when the DOM is ready
		$(document).ready(function(){
			//settings on top
			var domain = 'http://test.com/';
			var initialPosts = <?php echo get_posts(0,$_SESSION['posts_start']); ?>;
			//function that creates posts
			var postHandler = function(postsJSON) {
				$.each(postsJSON,function(i,post) {
					//post url
					var postURL = '' + domain + post.PostID;
					var id = 'post-' + post.PostID;
					
					//create the HTML
					$('<div></div>')
					.addClass('post')
 
					.attr('id',id)
					//generate the HTML
					.html('<tr><td>' + post.Post + ''*then I want my comments to loop thru here like comments.Comment*'</td></tr>')
 
					.click(function() {
						window.location = postURL;
					})
					//inject into the container
					.appendTo($('#posts'))
					.hide()
					.slideDown(250,function() {
						if(i == 0) {
							$.scrollTo($('div#' + id));
						}
					});
				});	
			};
			//place the initial posts in the page
			postHandler(initialPosts);
			//first, take care of the "load more"
			//when someone clicks on the "load more" DIV
			var start = <?php echo $_SESSION['posts_start']; ?>;
			var desiredPosts = <?php echo $number_of_posts; ?>;
			var loadMore = $('#load-more');
			//load event / ajax
			loadMore.click(function(){
				//add the activate class and change the message
				loadMore.addClass('activate').text('Loading...');
				//begin the ajax attempt
				$.ajax({
					url: 'indextest.php',
					data: {
						'start': start,
						'desiredPosts': desiredPosts
					},
					type: 'get',
					dataType: 'json',
					cache: false,
					success: function(responseJSON) {
						//reset the message
						loadMore.text('Load More');
						//increment the current status
						start += desiredPosts;
						//add in the new posts
						postHandler(responseJSON);
					},
					//failure class
					error: function() {
						//reset the message
						loadMore.text('Oops! Try Again.');
					},
					//complete event
					complete: function() {
						//remove the spinner
						loadMore.removeClass('activate');
					}
				});
			});
		});
	</script>