gistfile1.txt

public function byId(string $id)
{
    $query = [
        'source' => [
            'query' => [
                'query_string' => [
                    'fields' => ['id'],
                    'query' => $id,
                ],
            ],
        ],
    ];

    $body = $this->performSearch($query);
    $hits = new Hits($body['hits']);

    if ($hits->isEmpty()) {
        return null;
    }
}

private function performSearch(array $query): array
{
    $response = $this->client->request('POST', '_search/template', [
        'json' => $query
    ]);

    return json_decode($response->getBody()->getContents(), true);
}