php
{var $res = $_modx->resource}
{if !($snippet = $_modx->cacheManager->get('slider'~$res.id))}
    {'getImageList' | snippet : [
        'docid' => 1
        ,'tvname' => 'slider'
        ,'toJsonPlaceholder' => 'slider'
    ]}
    {var $snippet = $_modx->getPlaceholder('slider')}
    {set $null = $_modx->cacheManager->set('slider'~$res.id , $snippet, 0)}
{/if}

{foreach json_decode($snippet) as $slide}

{/foreach}

php
if ($id == 0) {
    return;
}

$cache = $modx->cacheManager->getCacheProvider($modx->getOption('cache_resource_key', null, 'default'));

$q = $modx->newQuery('modTemplateVarResource');
$q->leftJoin('modTemplateVar', 'modTemplateVar', [
  "modTemplateVar.id = tmplvarid"
]);
$q->where([
  'contentid' => $id,
  'modTemplateVar.type' => 'migx'
]);
$q->select($modx->getSelectColumns('modTemplateVar', 'modTemplateVar', '', ['name']));
if ($q->prepare() && $q->stmt->execute()) {
    $migxTvs = $q->stmt->fetchAll(PDO::FETCH_COLUMN);
    foreach($migxTvs as $tv) {
        $cache->delete($tv . $id);
    }
}