Getting data from imap_header()

Hi

I want to extract header data from a mail message using imap_header. This is what I hace currently:

if ($hdr = imap_header($mb,1)) {
while (list($key, $val) = each($hdr)) {
print "$key --> $valn";
}
}

which will get any variables out, but not return any of the arrays. How can I go through to contents of the arrays (such as from[]) as well?

Thanks

Mark