I have just completed a project that involved the integration of the 3.
SquirrelCart is a php/mysql shopping cart application, with control panel, heavy use of session variables, a lot of functions, templates, etc… pretty standard. There is almost no documentation for the code and the company does not provide any support for hacking it. I know it pretty well now though there are still occasional surprise.
Orbital is a payment gateway also known as Chase Paymentech. Their tech support was helpful but it was very difficult to get a test account from them for testing responses from their API. They normally don’t give them out to customers that are using certified shopping carts like SquirrelCart.
We needed to test Orbital’s responses with Order Motion(OM). Oribital is only authorizing the transaction and then OM completes it and controls inventory and has all kinds of fancy features. Their API is very thoroughly documented but they don’t have any quick start guides, and nothing about PHP. They run asp and both the help and control panel can only be viewed in Internet Explorer!
They did reluctantly provide some sample PHP code for the cURL request. We found that the OrderID element of the order request was required in order to match the order with the Orbital authorization. Also the authorization code from Orbital was 40 characters long and OM would only accept 30 max so they had to fix that at OM to accept more.
We also use Order Motion to retrieve inventory and past order information for the cart.
If you have questions or need help with any of these 3 solutions let me know.