protected function collectWorkerResults($sec = 0) {
		$this->respawnIfRequired();

		// dispatch signals
		pcntl_signal_dispatch();

		if (isset($this->workerProcesses) === FALSE) {
			throw new WorkerPoolException('There is no list of worker processes. Maybe you destroyed the worker pool?', 1401179881);
		}
		$result = SimpleSocket::select($this->workerProcesses->getSockets(), array(), array(), $sec);
		foreach ($result['read'] as $socket) {
			/** @var $socket SimpleSocket */
			$processId = $socket->annotation['pid'];
			$result = $socket->receive();

			$possibleArrayKeys = array('data', 'poolException', 'workerException');
			if (is_array($result) && count(($resultTypes = array_intersect(array_keys($result), $possibleArrayKeys))) === 1) {
				// If the result has the expected format, free the worker and store the result.
				// Otherwise, the worker may be abnormally terminated (fatal error, exit(), ...) and will
				// fall in the reapers arms.
				$this->workerProcesses->registerFreeProcessId($processId);
				$result['pid'] = $processId;
				$resultType = reset($resultTypes);
				// Do not store NULL
				if ($resultType !== 'data' || $result['data'] !== NULL) {
					array_push($this->results, $result);
				}
			}
		}
		// dispatch signals
		pcntl_signal_dispatch();

		$this->respawnIfRequired();
	}