src/Payum/Paypal/ExpressCheckout/Nvp/Api.php
public function doExpressCheckoutPayment(array $fields)
    {
        $fields['METHOD'] = 'DoExpressCheckoutPayment';

        $this->addVersionField($fields);
        $this->addAuthorizeFields($fields);

        return $this->doRequest($fields);
    }
public function doExpressCheckoutPayment(array $fields)
    {
        $fields['METHOD'] = 'DoExpressCheckoutPayment';

        $this->addVersionField($fields);
        $this->addAuthorizeFields($fields);

        return $this->doRequest($fields);
    }
Require: PAYMENTREQUEST_0_AMT, PAYMENTREQUEST_0_PAYMENTACTION, PAYERID, TOKEN

@param array $fields

@return array