Phalcon\Db\Adapter\MongoDB\Collection::aggregate PHP Method

    public function aggregate(array $pipeline, array $options = [])
    {
        $hasOutStage = Functions::isLastPipelineOperatorOut($pipeline);
        /* A "majority" read concern is not compatible with the $out stage, so
         * avoid providing the Collection's read concern if it would conflict.
         */
        if (!isset($options['readConcern']) && !($hasOutStage && $this->readConcern->getLevel() === ReadConcern::MAJORITY)) {
            $options['readConcern'] = $this->readConcern;
        }
        if (!isset($options['readPreference'])) {
            $options['readPreference'] = $this->readPreference;
        }
        if ($hasOutStage) {
            $options['readPreference'] = new ReadPreference(ReadPreference::RP_PRIMARY);
        }
        if (!isset($options['typeMap']) && (!isset($options['useCursor']) || $options['useCursor'])) {
            $options['typeMap'] = $this->typeMap;
        }
        $operation = new Aggregate($this->databaseName, $this->collectionName, $pipeline, $options);
        $server = $this->manager->selectServer($options['readPreference']);
        return $operation->execute($server);
    }