I’m not exactly sure what you’re trying to ask here. PHP is a programming language. Postman is a tool for making network calls. You can’t load a PHP script into Postman.
If you want to make the API calls you’re showing, you need to create the equivalent of your PHP script as a Postman call. This is pretty straightforward, except for the signature part. Otherwise you’re just building a POST request.
Hope that helps a little. Try breaking down your question to the simplest first step where you’re getting stuck.