ModX Revolution Caching Dynamicly Generated Placeholders - php

Question

How can I cache (using ModX's cacheManager), the dynamic placeholders i am generating here:
// recursive function to generate our un-ordered list of menu items
if(!function_exists('GenerateMenu')){
function GenerateMenu($level, $parent = 0, $wc, $wi, $we, $cs, $sc, $cl){
try {
$lvl = ++$level;
global $modx;
// Check for #1, should this be cached, #2 does it already exist in the cache
$cached = $modx->cacheManager->get('Navigator');
if($sc && isset($cached)){
// need to get the placeholders from cache - here somehow!
return $cached;
}else{
// get the site start
$siteStartId = $modx->getOption('site_start');
// Set our initial rows array
$rows = array();
// Run our query to get our menu items
$sql = 'Select `id`, `menutitle`, `uri`, `longtitle`, `parent`, `link_attributes`, `class_key`, `content`, `alias`, `introtext`
From `' . $modx->getOption(xPDO::OPT_TABLE_PREFIX) . 'site_content`
Where `deleted` = 0 AND `hidemenu` = 0 AND `published` = 1 AND `parent` = :parent
Order by `parent`, `menuindex`';
$query = new xPDOCriteria($modx, $sql, array(':parent' => $parent));
if ($query->stmt && $query->stmt->execute()) {
$rows = $query->stmt->fetchAll(PDO::FETCH_ASSOC);
}
// do some cleanup
unset($query, $sql);
// make sure we have some rows, and then build our html for the menu
if($rows){
// grab a count of our results
$rCt = count($rows);
$cls = ($lvl > 1) ? 'sub-item-' . $lvl : 'main-item-' . $lvl;
$ret .= ' <ul class="' . $cls . '" id="' . $cls . '-' . $parent . '">' . "\r\n";
for($i = 0; $i < $rCt; ++$i){
// if this resource is a WebLink, show the content in it, as the URL for the href tag, otherwise, use the resource's URI
$url = ($rows[$i]['class_key'] == 'modWebLink') ? $rows[$i]['content'] : '/' . $rows[$i]['uri'];
// Check for the site's start id, if true, show a "blank" link, otherwise show the $url
$showUrl = ($siteStartId == $rows[$i]['id']) ? '/' : $url;
$la = (strlen($rows[$i]['link_attributes']) > 0) ? ' ' . $rows[$i]['link_attributes'] : null;
// Set some dynamic placeholders, they can only be used ont he pages that contain this snippet
$modx->toPlaceholders(array('Title-' . $rows[$i]['id'] => $rows[$i]['longtitle'],
'MenuTitle-' . $rows[$i]['id'] => $rows[$i]['menutitle'],
'URL-' . $rows[$i]['id'] => $showUrl),
'link');
$ret .= ' <li class="' . $cls . '" id="' . $rows[$i]['alias'] . '">' . "\r\n";
$ret .= ' <a href="' . $showUrl . '" title="' . $rows[$i]['longtitle'] . '"' . $la . '>' . $rows[$i]['menutitle'] . '</a>' . "\r\n";
$ret .= GenerateMenu($lvl, $rows[$i]['id']);
// Check for a snippet, and render it
$it = $rows[$i]['introtext'];
if($cs && IsSnippet($it)){
// if we find a snippet in the Summary field, run it, and attach it to our output
preg_match('/\[\[!?(.*)\]\]/', $it, $sm);
$ret .= $modx->runSnippet($sm[1]);
// clean up
unset($sm);
}
$ret .= ' </li>' . "\r\n";
}
$ret .= ' </ul>' . "\r\n";
}
// clean up
unset($rows);
// Check to see if we should cache it, if so, set it to cache, and apply the length of time it should be cached for: defaults to 2 hours
if($sc){
// NEED TO SET THE PLACEHOLDERS TO CACHE SOMEHOW
$modx->cacheManager->set('Navigator', $ret, $cl);
}
// return the menu
return $ret;
}
} catch(Exception $e) {
// If there was an error, make sure to write it out to the modX Error Log
$modx->log(modX::LOG_LEVEL_ERROR, '[Navigator] Error: ' . $e->getMessage());
return null;
}
}
}

Answer 1

The easiest solution may be pdoTools which allows you to establish caching at run time.
http://www.shawnwilkerson.com/modx/tags/pdotools/
Also, I do not believe resource placeholders are cached which is the best place to have your items cahced:
case '+':
$tagName= substr($tagName, 1 + $tokenOffset);
$element= new modPlaceholderTag($this->modx);
$element->set('name', $tagName);
$element->setTag($outerTag);
$elementOutput= $element->process($tagPropString);
break;
From lines 455-461 of https://github.com/modxcms/revolution/blob/master/core/model/modx/modparser.class.php#L455
You may notice the other tag types have:
$element->setCacheable($cacheable);
I cover the parser in Appendix D of my book. I found some issues in it in 2011 which Jason corrected.

Answer 2

Move toPlaceholders() to the end of your script and instead cache the array of placeholder data:
// attempt to retrieve placeholders from cache
$placeholders = $modx->cacheManager->get('Navigator');
// if not in cache, run your snippet logic and generate the data
if (empty($placeholders))) {
$placeholders = array(
'myplaceholder' => 'placeholder data'
);
$modx->cacheManager->set('Navigator', $placeholders, $cl);
}
// set placeholders for use by MODX
$modx->toPlaceholders($placeholders);