I’ve dug around for hours in the SDK, but the API is overwhelming and doesn’t answer my question properly.
Does anyone have an example of how to create a merger (or variation), with PHP?
Well first I would use scratchpad to try an to the action you are doing in this case if its creating a variation.
Once you have that then its just a matter of creating the process in PHP to send the data to Amazon. I would try and use a simple call that can be reused such as the Reports API.
Here is more information about variation.