src/LaravelShop.php
public static function setGateway($gatewayKey)
    {
        if (!array_key_exists($gatewayKey, Config::get('shop.gateways')))
            throw new ShopException('Invalid gateway.');
        static::$gatewayKey = $gatewayKey;
        static::$gateway    = static::instanceGateway();
        Session::push('shop.gateway', $gatewayKey);
    }
public static function setGateway($gatewayKey)
    {
        if (!array_key_exists($gatewayKey, Config::get('shop.gateways')))
            throw new ShopException('Invalid gateway.');
        static::$gatewayKey = $gatewayKey;
        static::$gateway    = static::instanceGateway();
        Session::push('shop.gateway', $gatewayKey);
    }
Checkout current user's cart.