Snippet to flexibly cache any modElement instance

getCache.sample.html

<div>
<ul>
[[!getCache? &element=`getResources` &elementClass=`modSnippet` &cache_expires=`1200` &parents=`0` &depth=`0` &limit=`2` &tpl=`ulTpl` &sortby=`RAND()`]]
</ul>
</div>

getCache.snippet.php

<?php
$output = '';

$properties =& $scriptProperties;
$properties['element'] = empty($element) ? '' : $element;
$properties['elementClass'] = empty($elementClass) ? 'modChunk' : $elementClass;
$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);
$properties['cacheElementKey'] = $modx->resource->getCacheKey() . '/' . md5($modx->toJSON($properties)) . '/' . 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['cacheElementKey'], $properties['cacheOptions']);
    }
}
if (!isset($cached['properties']) || !isset($cached['output'])) {
    $elementObj = $modx->getObject($properties['elementClass'], array('name' => $properties['element']));
    if ($elementObj) {
        $elementObj->setCacheable(false);
        if (!empty($properties['toPlaceholder'])) {
            $elementObj->process($properties);
            $output = $modx->getPlaceholder($properties['toPlaceholder']);
        } else {
            $output = $elementObj->process($properties);
        }
    }

    if ($modx->getCacheManager()) {
        $cached = array('properties' => $properties, 'output' => $output);
        $modx->cacheManager->set($properties['cacheElementKey'], $cached, $properties[xPDO::OPT_CACHE_EXPIRES], $properties['cacheOptions']);
    }
} else {
    $properties = $cached['properties'];
    $output = $cached['output'];
}
$modx->setPlaceholders($properties, $properties['namespace']);
if (!empty($properties['toPlaceholder'])) {
    $modx->setPlaceholder($properties['toPlaceholder'], $output);
    $output = '';
}

return $output;
?>