code: public function lock($lockType)
      {
          if (!$this->isOpened()) {
              return false;
          }
  
          if ($this->options["blocking"]) {
              return flock($this->handle, $lockType);
          } else {
              $tries = 0;
              do {
                  if (flock($this->handle, $lockType | LOCK_NB)) {
                      return true;
                  } else {
                      ++$tries;
                      usleep(self::LOCK_RETRY_WAIT);
                  }
              } while ($tries < self::LOCK_MAX_TRIES);
  
              return false;
          }
      }
docs: Obtains a file lock
  
  @param int $lockType Lock type PHP constant
  @return boolean true on successful lock, false otherwise