Unable to write 0 value on LDAP attribute

Writing 0, NULL or empty value into a LDAP will delete the attribute and doesn't check if the delete was done.

Based on this issue http://us2.php.net/manual/fr/function.ldap-mod-del.php#9706 , the fields without EQUALITY definition cannot be changed

The LDAP error: "Inappropriate Matching".

For fixing I changed the method writeAttributes from LDAPInterface class:

function writeAttributes($dn, $attributes) {
  foreach ($attributes as $key => $cur_val) {
    if ($cur_val === '') {
      $old_value = $this->retrieveAttribute($dn, $key);
      if (isset($old_value)) {
        $success = @ldap_mod_del($this->connection, $dn, array($key => $old_value));
      }
      //http://www.php.net/manual/en/function.ldap-mod-del.php#9706
      if($success){
        unset($attributes[$key]);
      }
    }
    //Encodes password for use in Active Directory // http://drupal.org/node/339821
    if ($key == "unicodePwd") {
      $cur_val = "\"" . $cur_val . "\"";
      $attributes[$key] = mb_convert_encoding($cur_val, "UTF-16LE");
    }
    if (is_array ($cur_val)) {
      foreach ($cur_val as $mv_key => $mv_cur_val) {
        if ($mv_cur_val == '') {
          unset($attributes[$key][$mv_key]);
        }
        else {
          $attributes[$key][$mv_key] = $mv_cur_val;
        }
      }
    }
  }
  if($attributes){
    return ldap_modify($this->connection, $dn, $attributes);
  }
  return TRUE;
}