Mailgun\Mailgun::__construct PHP Method

    public function __construct($apiKey = null, HttpClient $httpClient = null, $apiEndpoint = 'api.mailgun.net', ResponseDeserializer $deserializer = null, HttpClientConfigurator $clientConfigurator = null, RequestBuilder $requestBuilder = null)
    {
        $this->apiKey = $apiKey;
        $this->restClient = new RestClient($apiKey, $apiEndpoint, $httpClient);
        if (null === $clientConfigurator) {
            $clientConfigurator = new HttpClientConfigurator();
            /*
             * To be backward compatible
             */
            if ($apiEndpoint !== 'api.mailgun.net') {
                $clientConfigurator->setEndpoint($apiEndpoint);
            }
            if ($httpClient !== null) {
                $clientConfigurator->setHttpClient($httpClient);
            }
        }
        $clientConfigurator->setApiKey($apiKey);
        $this->httpClient = $clientConfigurator->createConfiguredClient();
        $this->requestBuilder = $requestBuilder ?: new RequestBuilder();
        $this->deserializer = $deserializer ?: new ModelDeserializer();
    }

 /**
  * MailgunManager constructor.
  * @param string $apiKey
  * @param string $domain
  * @throws MailWrapperSetupException
  */
 public function __construct($apiKey, $domain)
 {
     if (!$apiKey || !$domain) {
         throw new MailWrapperSetupException('API Key and Domain must be provided');
     }
     $this->domain = $domain;
     $this->apiKey = $apiKey;
     // fixes for Puli factory breakages
     $client = null;
     if (class_exists('\\Http\\Adapter\\Guzzle6\\Client')) {
         $guzzleClient = new Client();
         $client = new Guzzle6Client($guzzleClient);
     } else {
         if (class_exists('\\Http\\Adapter\\Guzzle5\\Client')) {
             $guzzleClient = new Client();
             $factory = new GuzzleMessageFactory();
             $client = new Guzzle5Client($guzzleClient, $factory);
         }
     }
     parent::__construct($apiKey, $client);
 }