Hopefully the code below help you to loop through references with LDAP3 servers. It took me a significant amount of time to figure out how this thing works and now I have successfully used this with Active Directory to loop through severial subdomains.

Special thanks to Stig Venaas who helped me to get started. (the original problem was that ldap_parse_reference function was missing in Windows builds. At least it will now work with Windows PHP versions 5.1.0-DEV and higher after I made a bug report)

function crawlRefs($user, $passw, $host, $dn, $port, $filter) {

  //Create the basic connection for fetching referrals
  $adConn = ldap_connect($host, $port) or die("System couldn't connect!");
  ldap_set_option($adConn, LDAP_OPT_PROTOCOL_VERSION, 3) or die ("System couldn't make first protocol option setting!");
  ldap_set_option($adConn, LDAP_OPT_REFERRALS, 0) or die ("System couldn't make second protocol option setting!");
  $bd = ldap_bind($adConn, $user, $passw) or die ("System couldn't bind the connection!");
  $search = ldap_search($adConn, $dn, $filter);

  //Find referrals
  $ref = ldap_first_reference($adConn, $search);
  while ($ref) {
    if (ldap_parse_reference($adConn, $ref, $referrals)) {
      while ($referral = array_shift($referrals)) {
        echo $referral . "<br>\n";
      }
    }
  $ref = ldap_next_reference($adConn, $ref);
}