You could theoretically set up both gateways, but most merchants will only need to set up one. Let’s look at Authorize.net first.

As with most elements, you will want to make sure the Enabled dropdown is set to Yes in order to display the option on the frontend. You can then edit the title which is how the method will appear to the customer on the payment page.

You will then need to enter your API Login ID and Transaction Key in order to integrate the site with your Authorize.net account. You can find this information in your Account Settings in the Authorize.net account. You can select whether you want customers’ cards only to be authorized on checkout, or whether the customers’ cards will be captured simultaneously on checkout.

You can then set up the status you want the orders placed with this method to be created with. In this example we have the orders set to be created with a status of Processing.

The next dropdown allows you to specify whether you want the site to be in Test or Live mode. Before you take your site live you will want to make sure you set this dropdown to No.

The Gateway URL for where Magento sends order information to Authorize.net comes prepopulated. The Debug dropdown determines whether all requests between Magento and Authorize.net will be saved in the Magento database.

The next dropdown allows you to specify whether you want Authorize.net to send emails to your customers on the completion of checkout. This dropdown Does Not influence the transactional emails sent from Magento, only the emails sent from your Authorize.net account.

If want Authorize.net to also send emails to you, the Store Owner, you will need to enter the email address associated with your account in the Merchant’s Email field.

You can determine which types of Credit Cards you will accept, and whether or not your customers will be required to enter a Card Verification number during checkout.

As with all Payment Methods, you can set the countries and order amount filters, to determine which custoemrs will be allowed to use this Payment Method. Finally you can set the sort order of Authorize.net in relation to the other payment methods offered.

As always, remember to select Save Config and you will be set up to accept credit cards using your Authorize.net account.

Payflow Pro is set up in much the same way as Authorize.net. Enter your account information, set the Enabled status to Yes, enter the Title, payment action, and new order status. Magento will prepopulate several of the other fields as well, configured for the ideal use of this Payment Method. Set your filters and the position you want to display the Payflow option to your customers with.

Transaction Version
Receipt Page
Response/Receipt URLs
Silent Post URL
Receipt Page
Relay Response
Direct Response

But now getting error:

Invalid HTTP response version:

“Unable to read response or response is empty”

with Authorize.net. Can’t get PayPal Express to work either…

WorldPay
SECPay
VeriSign
Secure Trading

Where can I find docs to do that ?