code: public function skip($count)
      {
          if ($this->count - $this->index < $count) {
              throw $this->createException("Cannot skip {$count} characters");
          }
          
          $this->index += $count;
          $this->current = $this->computeCurrent();
      }
docs: 指定された文字数だけ index を進めます.
  @param int $count 文字数