<?php

/**
 * This file handles caching headers.
 *
 * Scripts that include this file should set "template" variables
 *
 * $MODIFIED - when the page was last modified, default is time().
 * $CACHE_MAXAGE - maximum age in seconds, default is 900 (15 minutes).
 * $CACHE_SCOPE - whether this can be publicly or privately cached, default is "public".
 */

// phps "r" date format puts +0000 for timezone
if (!defined('RFC_DATE')) {
  define('RFC_DATE', 'D, d M Y H:i:s \G\M\T');
}

// set defaults
if (!isset($CACHE_MAXAGE)) {
  $CACHE_MAXAGE = -1;
}
if (!isset($CACHE_SCOPE)) {
  $CACHE_SCOPE = 'public';
}
if (!isset($MODIFIED)) {
  $MODIFIED = filemtime($_SERVER['SCRIPT_FILENAME']);
}


if ($CACHE_MAXAGE >= 0) {
  // do these before if-modified-since, so that response can also be cached
  header('Cache-Control: ' . $CACHE_SCOPE . ', max-age=' . $CACHE_MAXAGE);
  header('Expires: ' . gmdate(RFC_DATE, time() + $CACHE_MAXAGE));
}

// make this cacheable
header('Last-Modified: ' . gmdate(RFC_DATE, $MODIFIED));