Webhook json format

I've been battling with exporting the name and email collected from my chatbot using webhooks.
I have successfully assigned both variables and set the proper value in my chatbot. The webhook also connects to my php script successfully. But I am not able to retrieve the values for "username" and "password" sent in the json POST request.
Please can you provide a format for the json request so I know how to retrieve the values.
Thanks