Hello folks... 
Imap sort works only with small mailbox...

<--- snip --->
  $newstrm = imap_open ($ms.$selectedmb, $usr, $usrpwd) or die ("cant connect: ".imap_last_error());
  switch ($sortby) {
    case "date":
  $sorted_headers = imap_sort($newstrm,SORTDATE, $rev_flag,'');
      break;
    case "subject":
  $sorted_headers = imap_sort($newstrm,SORTSUBJECT, $rev_flag,'');
      break;
    case "tag":
      if ($tag == "From") {
  $sorted_headers = imap_sort($newstrm,SORTFROM, $rev_flag,'');
      } else {
  $sorted_headers = imap_sort($newstrm,SORTTO, $rev_flag,'');
      }
      break;
    case "size":
  $sorted_headers = imap_sort($newstrm,SORTSIZE, $rev_flag,'');
      break;
  }
  while (list(,$qq) = each($sorted_headers)) {
    $header = imap_headerinfo($newstrm, $qq);

   ....>>> etc
<--- snip --->
the sort sequence returned by imap_sort is incorrect for any mailbox where there is more than 10 emails in the mailbox, and especially if there is a mix of "R" and "U" type of unread.
The function appears to sort partly by new, and then old, and then both...

<========== php compiled with ========
 './configure' '--with-mysql=/usr/local/mysql' '--with-xml' '--with-apache=../apache_1.3.19/' '--with-imap=/usr/local/imap' '--enable-track-vars' 

<======== imap specs ===========
compiled from :

imap-2001.BETA.SNAP-0106191041.tar

<========= hardware ============>

intel Pentium 4 1.3 Ghz
640 meG ram
400MHZ BUS MOTHERBOARD