Ok, try this (omit the spaces from the tags, obviously, and this is all assuming that the text field for the username is called "username" and the text field for the password is called "password"):
< ?php
switch($username) {
case "Bob":
if ($password == "bob") {
include("bob.php");
} else {
print "Bad password."
}
break;
case "Cedrick":
if ($password == "cedrick") {
include("cedrick.php");
} else {
print "Bad password."
}
break;
}
? >
If the include statement doesn't work for you, you can use this instead:
header("Location:
http://www.yoursite.com/bob.php");
If you do use header() instead of include(), you have to put the PHP code at the very, very top of the page, even above the < html> tag.
Hope this works.

If it doesn't, let me know.