code: function getSibling($offset = 1) {
  		$index = $this->index() + $offset;
  		if (($index >= 0) && ($index < $this->parent->childCount())) {
  			return $this->parent->getChild($index);
  		} else {
  			return null;
  		}
  	}
docs: Get sibling node
  @param int $offset Offset from current node
  @return DomNode Null if not found