Stupid people write unclear questions!
I meant -- I guess incorrectly -- that this is not a redirect in the HTTP sense of it. There will not be a 301, 302 or 303 HTTP response to the user's POST request. The user will not be sent to interact directly with script 2. All of this action is happening behind the scenes. The user interacts with script 1 from start to finish, but at a certain point, script 1 sends a POST request to script 2.
Edited to add: Just re-read the original question. I did specifically ask about how to have one script send a POST request to a second script, so I'm really not sure how that was an "unclear question". I think you read into the question something that I didn't actually ask.