Simple Ajax Switch as a snippet for modx Revolution

simpleAjaxSwitch.php

/* Simple Ajax Switch Snippet for modx Revolution
 *
 * Checks whether the page was requested via Ajax and depending on this outputs different chunks.
 * Save it as a snippet called simpleAjaxSwitch
 * 
 * Adapted from here:
 * http://forums.modx.com/thread/15204/change-template-on-the-fly#dis-post-82222
 * Thanks to Bruno!
 *
 * Usage in Template:
 * [[!simpleAjaxSwitch? 
 * &ajaxChunk=`ajaxTemplate` 
 * &defaultChunk=`baseTemplate`
 * &cache=`1`
 * ]]
 */


<?php
$output = '';   

if(isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest'){

  $properties =& $scriptProperties;
  $properties['cache'] = isset($cache) ? (boolean) $cache : (boolean) $modx->getOption('cache_resource', $properties, false);
  $properties[xPDO::OPT_CACHE_KEY] = $modx->getOption('cache_resource_key', $properties, 'default');
  $properties[xPDO::OPT_CACHE_HANDLER] = $modx->getOption('cache_resource_handler', $properties, 'xPDOFileCache');
  $properties[xPDO::OPT_CACHE_EXPIRES] = (integer) $modx->getOption(xPDO::OPT_CACHE_EXPIRES, $properties, 0);

  if ($properties['cache']) {
    $properties['cachePageKey'] = $modx->resource->getCacheKey() . '/' . md5(implode('', $modx->request->getParameters()));
    $properties['cacheOptions'] = array(
      xPDO::OPT_CACHE_KEY => $properties[xPDO::OPT_CACHE_KEY],
      xPDO::OPT_CACHE_HANDLER => $properties[xPDO::OPT_CACHE_HANDLER],
      xPDO::OPT_CACHE_EXPIRES => $properties[xPDO::OPT_CACHE_EXPIRES],
    );
  }

  $cached = false;
  if ($properties['cache']) {
    if ($modx->getCacheManager()) {
      $cached = $modx->cacheManager->get($properties['cachePageKey'], $properties['cacheOptions']);
    }
  }
  
  if (empty($cached) || !isset($cached['properties']) || !isset($cached['output'])) {
    $output = $modx->getChunk($ajaxChunk,$_REQUEST);
    if ($properties['cache'] && $modx->getCacheManager()) {
      $cached = array('properties' => $properties, 'output' => $output);
      $modx->cacheManager->set($properties['cachePageKey'], $cached, $properties[xPDO::OPT_CACHE_EXPIRES], $properties['cacheOptions']);
    }    
  } else {
    $properties = $cached['properties'];
    $output = $cached['output'];
  }

} else {
  $output = $modx->getChunk($defaultChunk); 
}
 
 
return $output;