Cartalyst\Stripe\Config::__construct PHP Method

    public function __construct($version, $apiKey, $apiVersion)
    {
        $this->setVersion($version);
        $this->setApiKey($apiKey ?: getenv('STRIPE_API_KEY'));
        $this->setApiVersion($apiVersion ?: getenv('STRIPE_API_VERSION') ?: '2015-03-24');
        if (!$this->apiKey) {
            throw new \RuntimeException('The Stripe API key is not defined!');
        }
    }