fopen with POST method

[Anon]

Hello,

   I would like to know if it is possible to use the function fopen() from PHP with POST method.
   When we use GET, it is very easy, we just add the values in the URL like this: anypage.php?id=5&name=YourName&etc=etc
   How should I do to open with POST without asking the user to POST any data?
   I need this to calculate shipping rates to CORREIOS (brazilian FedEx). They only accept POST method in the REMOTE shipping rate calculator.

Thanks