gistfile1.txt

$script = new \Elastica\Script('doc["skus.stock"].values');

        $scriptAggr = new \Elastica\Aggregation\Terms('script_aggr');
        $scriptAggr->setScript($script);
        $scriptAggr->setParam('size', 100000);

        $nestedAggr = new \Elastica\Aggregation\Nested('nested_sku_aggr', 'skus');

        $nestedAggr->addAggregation($scriptAggr);