You're going in the wrong direction. That's a header that a user agent (i.e. web browser) would throw at the web server from the other side of the fence.
You can send the username and password like this:
http://uername:password@server.domain.com
but that will likely show their username and password.
To make it work, you can make a main login page that does a "header ("location: http://server.domain.com/index.html");
So their username and password disappear after the blind login.