John Conde has shared his multi-part guide to getting your application integrated with the popular payment service Authorize.net.

As an Authorize.Net blogger, I decided to write a series of articles that outlined not only the basics of handling an ecommerce transaction, but also included some best practices as well. These were demonstrated using a web-based payment form that when complete forms a real-world, production ready solution. Since there was a lot of ground to cover, I broke the tutorial into eleven parts.

Parts of the series cover topics like:

• reading/sanitizing data
• handling validation errors
• preventing duplicate submissions
• preventing automated form submissions

For those that want to jump straight into the code, he also links to his sample payment form and the Authorize.net PHP SDK.

In a recent post Eran Galperin takes a look at the PayPal API and breaks it down into smaller, easy to digest chunks to show you how to you can implement it in your application. Be warned, though - he mentions that it's the "among the worst API he's ever had to deal with" for several reasons.

PayPal is the most popular platform for receiving online payments. The relative ease of opening a PayPal account and receiving payments compared to opening a merchant account for a traditional payment gateway is the number one reason, and another is the comprehensive API they provide for their payment services. [...] There doesn't seem to be any better alternatives currently, so hopefully this guide will help ease the pain for some of you out there taking your lumps working the API into your applications.

Eran starts with a look at some of the different payment options, express, direct, recurring and mass, and what they're good for. From there, it's off to the code with his tool of choice being curl to make it simpler to make requests with headers, content and fetch the response message. He's put together a little custom function to make it easier to reuse. As an example, he shows how to make an Express Checkout request by grabbing a token and redirecting to the PayPal site for handling.

On the 9Lessons blog today Srinivas Tamadashows you how to create a simple PayPal interface between their API and your site to make accepting payments easier.

I received a tutorial requests from my reader that asked to me how to implement payment gateway system with Paypal API. In this post I want to explain how to work with Paypal Sandbox test accounts for payment system development and sending arguments while click buy now button. It's simple and very easy to integrate in your web projects.

He includes the SQL to create a basic database for storing product and sales information (as well as a bit of user data linked to them) as well as instructions on creating the accounts you'll need on the PayPal side. The script creates a form that takes the payment information and pushes it to a script on the PayPal side for validation and charging.

In a recent post Matt Williams shares how to integrate your application with the PayPal IPN payment gateway service.

PayPal has a huge API reference to integrate it's services into any website. But from personal experience I found that the theory is far more simple than the practice. There are various methods to implement PayPal's services including Soap webservices with 'Express Checkout' and 'Website Payment Pro'. This tutorial will focus on 'Website Payment Pro' and the 'IPN' event listener.

He shows how to send the information as a POST request in one of two ways - as a standard form submission kind of POST and from a script opening a direct socket to the PayPal server and sending over a well-formed request.

Matthew Turland has posted the eighth part of his detailed series looking at the feature set that the Magento e-commerce software has to offer to the Blue Parabola blog. This new post looks at the "payment offering" features.

Features mentioned in this post include:

• Customer Store Credits Feature
• Integrated with Amazon Payments
• Gift Certificates/Cards (Physical and Virtual)
• Integrated with Google Checkout
• Accept Purchase Orders
• Payment Extensions Available through Magento Connect

Check out the full post for more and descriptions of each.

Juozas Kaziukenas points out a new class in his latest blog post that can be used to make secure connections over to PayPal (encrypted) using their Encrypted Website Payment method.

In my situation, PayPal is only used to pay for orders - cart and order setup is done in our shop, so I do not want to have additional problems with users changing orders numbers, amount to be paid, etc. [...] Only PayPal knows how to decrypt it, because it uses public key encryption technology (you need to upload your certificate in PayPal account).

Some sample usage code is included as is a link to the class itself. His example takes a payment transaction including the item name, amount and currency type and sends it off to the PayPal servers in a connection protected by certificates.

Following up from a previous entry, Mike Willbanks has posted some clarifications on points previously made and the highlights on what he thinks a good framework should entail.

I decided to clarify and also explain some of my thoughts and ideas that an e-commerce framework should hold. These thoughts and ideas may be a little rough around the edges but I wanted to give a definition to the meaning of what I feel a framework is in this case as well as items that would potentially be a part of this framework.

Some of his requirements are things like reusable design, useful/easy to use components, functionality for both payment processing and courier handling as well as a catalog system to help manage items.

The Zend Developer Zone has a nwe post that announces the release of the first version of an API created to interface your PHP scripts with the Website Payments Pro API from Paypal - phpPaypalPro.

It is a framework developed in PHP5 that integrates easily with the Website Payments Pro API from Paypal. Currently it supports 4 major operations available from the Website Payments Pro SOAP 1.1 API. It has taken advantage of the built-in SOAP extension available natively in PHP5 to generate the requests and interprets the responses to and from the Website Payments Pro SOAP-based web service.

Current operations supported include: DoDirectPayment, SetExpressCheckout, GetExpressCheckoutDetails and DoExpressCheckoutPayment and you can get more information about other functionality from the project's documentation. Be sure to check out the sample script and the full SourceForge page for even more Paypal interface goodness.