Max Aggregation

More info about max aggregation is in the official elasticsearch docs

A single-value metrics aggregation that keeps track and returns the maximum value among the numeric values extracted from the aggregated documents.

Simple example

{
    "aggregations" : {
        "max_price" : { "max" : { "field" : "price" } }
    }
}

And now the query via DSL:

$maxAggregation = new MaxAggregation('max_price', 'price');

$search = new Search();
$search->addAggregation($maxAggregation);

$queryArray = $search->toArray();