App\Ninja\PaymentDrivers\PayPalExpressPaymentDriver::paymentDetails PHP Method

    protected function paymentDetails($paymentMethod = false)
    {
        $data = parent::paymentDetails();
        $data['ButtonSource'] = 'InvoiceNinja_SP';
        $data['solutionType'] = 'Sole';
        // show 'Pay with credit card' option
        return $data;
    }