code: public function getNumProcessedItems($tickType = null)
      {
          if (null !== $tickType) {
              return (array_key_exists($tickType, $this->numProcessedItems))
                  ? $this->numProcessedItems[$tickType]
                  : 0;
          }
          else {
              return array_sum($this->numProcessedItems);
          }
      }
docs: Return the number of items processed, including failed/succeeded
  
  @param int $tickType  Tick::SUCCESS, Tick::FAIL, Tick::SKIP, or null for all
  @return int