Horde_Imap_Client_Ids::isEmpty PHP Method

    public function isEmpty()
    {
        return is_array($this->_ids) && !count($this->_ids);
    }

 /**
  * Resolves an IDs object into a list of IDs.
  *
  * @param Horde_Imap_Client_Mailbox $mailbox  The mailbox.
  * @param Horde_Imap_Client_Ids $ids          The Ids object.
  * @param integer $convert                    Convert to UIDs?
  *   - 0: No
  *   - 1: Only if $ids is not already a UIDs object
  *   - 2: Always
  *
  * @return Horde_Imap_Client_Ids  The list of IDs.
  */
 public function resolveIds(Horde_Imap_Client_Mailbox $mailbox, Horde_Imap_Client_Ids $ids, $convert = 0)
 {
     $map = $this->_mailboxOb($mailbox)->map;
     if ($ids->special) {
         /* Optimization for ALL sequence searches. */
         if (!$convert && $ids->all && $ids->sequence) {
             $res = $this->status($mailbox, Horde_Imap_Client::STATUS_MESSAGES);
             return $this->getIdsOb($res['messages'] ? '1:' . $res['messages'] : array(), true);
         }
         $convert = 2;
     } elseif (!$convert || !$ids->sequence && $convert == 1 || $ids->isEmpty()) {
         return clone $ids;
     } else {
         /* Do an all or nothing: either we have all the numbers/UIDs in
          * memory and can return, or just send the whole ID query to the
          * server. Any advantage we would get by a partial search are
          * outweighed by the complexities needed to make the search and
          * then merge back into the original results. */
         $lookup = $map->lookup($ids);
         if (count($lookup) === count($ids)) {
             return $this->getIdsOb(array_values($lookup));
         }
     }
     $query = new Horde_Imap_Client_Search_Query();
     $query->ids($ids);
     $res = $this->search($mailbox, $query, array('results' => array(Horde_Imap_Client::SEARCH_RESULTS_MATCH, Horde_Imap_Client::SEARCH_RESULTS_SAVE), 'sequence' => !$convert && $ids->sequence, 'sort' => array(Horde_Imap_Client::SORT_SEQUENCE)));
     /* Update mapping. */
     if ($convert) {
         if ($ids->all) {
             $ids = $this->getIdsOb('1:' . count($res['match']));
         } elseif ($ids->special) {
             return $res['match'];
         }
         /* Sanity checking (Bug #12911). */
         $list1 = array_slice($ids->ids, 0, count($res['match']));
         $list2 = $res['match']->ids;
         if (!empty($list1) && !empty($list2) && count($list1) === count($list2)) {
             $map->update(array_combine($list1, $list2));
         }
     }
     return $res['match'];
 }