getJSON函数，从多个mysql查询返回编码数组

I'm wondering if it is possible to combine many queries into one array and return it. The problem is that some of those queries already are arrays...here's what I mean:

JS:

function getNews() {
  $.getJSON(serviceURL + 'getmainnews.php', function(data) {
    $('#fnews li').remove();
    daily = data.items;
      $.each(daily, function(index, mnews) {
        //append the data to listview
      });
    });

Here is the php file with the queries:

<?php
  include 'connect_to_mysql.php';
  mysql_query("SET NAMES UTF8");
  $day = mysql_query("SELECT * FROM basket_news WHERE topic='daily' ORDER BY id DESC LIMIT 1");
  $daily = array();
  while ($r = mysql_fetch_assoc($day)){
    $daily[] = $r;
  }

  $sql = mysql_query("SELECT * FROM basket_news WHERE topic='' ORDER BY id DESC"); 
    $mainnews = array();
    while ($r = mysql_fetch_assoc($sql)){
      $mainnews[] = $r;
    }
?>

If I have more queries like this, how can I gather them together to be able to do something like:

echo json_encode(array("items" => $daily, "allitems" => $mainnews));

I understand that $daily has a LIMIT 1 with it, but others like $mainnews will be big arrays. How would I set up the PHP echo and get it back in JS? I guess if all else fails, I could do multiple ajax calls but that would be a waste...