I would recommend using the header() function with the Location header. That sounds like what you're after.
Example:
(code to parse and secure input first)
if (certaininput) {
header("Location: http://www.page.here");
} elseif (otherinput) {
header("Location: http://www.someotherpage.here");
}
..and so on.
The same caveat applies as always, though - when sending headers to the browser, be sure no other output (HTML or otherwise) is passed to the browser before those header lines.