api dolar

public function getDolar_api(){
        $client = new \GuzzleHttp\Client();
        $request  = $client->request('GET', 'http://s3.amazonaws.com/dolartoday/data.json');
        $response = $request->getBody()->getContents();
        $tasas = json_decode($response);

        if(is_null($tasas))
            return null;

        return $tasas->USD->promedio_real;
}