question about sensms http interface

Hi,

I would like to program a web page to send sms. I had program a page in
php, with forms etc... The only way to do that in the userguide is by
GET request and the url is like this :
http://smsbox.host.name:13013/cgi-bin/sendsms.php?
username=foo&password=bar&to=0123456&text=Hello+world
but i don't want that people can read the username, the password and the port of the smsbox
.
How can do ? Is it possible to do a POST request ? Or if the smsbox and the appache server
are in the same computer to do a command ?

Thanks a lots.
Regards.

Jérémie from Libreville