I need recommendations for how to build a form/frame that could be embedded within any website that could be used to process a registration and payment.
I know at one time iFrames were designed for this purpose but there are much better ways of doing this and that's where I'm looking for insight.
Here's the back story.
I have a stand-alone registration website that handles very complex needs (housing, group payments, custom questions, multiple payment methods, etc.). For complex events, they really need to come to my site. But for some events that are quite simple, I could write a basic API that would allow interaction between the client site and my site by means of an API.
How I envision it working.
What I would like is that I could give some simple code to a client who would place that code on their page. That code would initiate a command that would read the data from my site via an API interface. Any interaction on the client side would be processed back to my site. So it would look like they never left the client site.
Any expert advice for how I should proceed with this would be appreciated. Thanks.