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

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

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

use GuzzleHttp\Client;
use Namshi\Cuzzle\Subscriber\CurlFormatterSubscriber;
use Monolog\Logger;
use Monolog\Handler\TestHandler;

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

$client  = new Client(); //initialize a Guzzle client
$client->getEmitter()->attach(new CurlFormatterSubscriber($logger)); //add the cURL formatter subscriber

$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"