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Working With Server Integration Method (SIM) Payment Gateway, Part 2: Proper Form Design

The most important step in using the Server Integration Method (SIM) payment gateway is properly designing your ordering system / shopping cart, well before you ever request payment.

Let me repeat that: If you want a secure, sensible and error-free checkout experience, you need to design a storefront that makes those things possible. Just as it is with building a house, if the foundation is crap, it won’t stand up to a storm.

I promised in a recent post to show how to properly send transaction requests to SIM. So, here’s the first step: An overview of best practices, and a sample order form that follows them.

Let me offer this, right up front: If your Web sales are casual — say, you want to let people buy annual banquet tickets online, or you sell a couple coffee mugs / T-shirts each week — you should seriously consider using a third-party turnkey solution.

The legal, practical and technical requirements of running your own ecommerce solution generally aren’t worth the hassle if you’re not doing a significant volume of sales.

I like EventBrite for handling ticket sales and CafePress for selling merchandise. There are other storefront options out there, but those are ones I have used and found reliable.

That said, there are circumstances where low-volume sellers still need custom ecommerce solutions. So, with that in mind, let’s cover the basics of making a secure, simple ordering system.
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Working With The Server Integration Method (SIM) Payment Gateway, Part 1: Don’t Use JavaScript

I got an email a few days ago from a reader seeking help with the Server Integration Method (SIM) credit card payment gateway.

Specifically, he was asking how he could use JavaScript to pass a calculated total to a PHP page that contains the SIM code.

  • A customer chooses a series of options from some select lists, radio buttons and the like;
  • the page calculates an order total;
  • the end user hits a submit button;
  • the results are posted to the SIM processing page, which acts as a “confirmation page”; and
  • The customer presses another button, which takes him to to provide payment info and actually charge the card.

You can see an approximation of what I’m talking about here: The questioner’s form is similar to this approximation in function.

I will show how to properly customize a SIM form, and submit payment requests to via SIM, in an upcoming post. This post explores why it’s a terrible idea to process order forms with JavaScript. That is, it’s about the wrong way to use SIM. Stay tuned for the right way.

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