use Namshi\Cuzzle\Formatter\CurlFormatter;
use GuzzleHttp\Message\Request;

$request = new Request('GET', 'example.local');
$options = [];

echo (new CurlFormatter())->format($request, $options);

use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use Namshi\Cuzzle\Middleware\CurlFormatterMiddleware;
use Monolog\Logger;
use Monolog\Handler\TestHandler;

$logger = new Logger('guzzle.to.curl'); //initialize the logger
$testHandler = new TestHandler(); //test logger handler
$logger->pushHandler($testHandler);

$handler = HandlerStack::create();
$handler->after('cookies', new CurlFormatterMiddleware($logger)); //add the cURL formatter middleware
$client  = new Client(['handler' => $handler]); //initialize a Guzzle client

$response = $client->get('http://google.com'); //let's fire a request

var_dump($testHandler->getRecords()); //check the cURL request in the logs, 
//you should see something like: "curl 'http://google.com' -H 'User-Agent: Guzzle/4.2.1 curl/7.37.1 PHP/5.5.16"