<?php
  $uid = $_SESSION['user_id'];
  $result = $db->get('SELECT ...');

  header ("Expires: Mon, 26 Jul 1990 05:00:00 GMT");
  header ("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
  header ("Cache-Control: no-cache, must-revalidate");
  header ("Pragma: no-cache");
  header ("Content-type: application/javascript");

  echo 'var myData = '.json_encode($result);

?>