Thank you for the opportunity to present on this. I hope you have found it useful.
I have put the slides and the full demo application in the repositories here:https://github.com/academe/OmniPay-PHPNE-talkhttps://github.com/academe/OmniPay-SagePay-Demo
The run the demo scripts, you will need to run `composer install` to pull in OmniPay, the SagePay library and its few dependencies. There is one very simple database table to create and your database auth details to add to the .env file. You will, of course, need a test SagePay account, but that should be it to be up and running. I've commented the scripts to explain what is happening at each stage.
Have fun, and do ask if you have any questions.