PHP autopost

How do I post data from a PHP script? Transparently for the user. He will fill in a form, then my PHP will retrieve some data from a database, and then I want to automaticaly submit user's data combined with some of the database's results to another page, using POST. Also, some of that data is sensible, so I can't just print it on the output html and just use some javascript to submit it.

How do I do that?

... Retrieve the data in the code that deals with the user input after he submits the form?
Seriously, what kind of a retard are you?