code: public function add(IComparable $pSource)
      {
          $hash = $pSource->getHashCode();
          if (!isset($this->items[$hash])) {
              $this->items[$hash] = $pSource;
              $this->keyMap[count($this->items) - 1] = $hash;
          }
      }
docs: Add HashTable item.
  
  @param IComparable $pSource Item to add