This will redirect the client to /foo.php.
The method will take care of adding the right hostname as
required by RFC 2616.
Parameter
string $url - the new URL, where
to client should be redirected to.
Note
This function can be called
statically.
Avoid sending any kind of data to the client before calling
redirect().
The location header requires an absolute URL. If not given,
redirect() tries to build one from
$url. So if the redirect fails,
set the absolute URL manually as argument.