How to use Envato API in PHP or ASP.net?
It really depends on what you are planning to do with it, all information about the available API requests can be found over here, with PHP you would be able to use CURL to send the request to the Envato API.
This guide will give you some basic info about how to use curl. After you have sent your CURL request to the Envato API, the API will response with a JSON message, inside your script you will need to do something with this JSON message, like converting it to a PHP array by using json_decode
Hope this will get you started
I wrote a simple guide on how to use it here: