If you mean posted by submitting a form from an ordinary browser,
then no--but of course it's up to you how little data the PHP page
that receives the POST actually sends back.
OTOH, if you aren't limited to just a browser, you can certainly
connect to the server just by opening a socket to port 80 on
the machine, and send and receive http as invisibly as you
care to make it. There's even a column somwhere here about
doing this.