致命错误: Call to a member function toArray() on null

			$articles['data'][$k]['category_name'] = cache('categorys')[$v['category_id']]['name'];
		}
		return $articles;
	}
	/**
	* 获取文章详情
	*/
	function get_details($id){
		$result = $this->get($id);
		$article = $result->toArray();
		$next = $this->where('id','<',$id)->where('category_id',$article['category_id'])->order('id desc')->find();
		$prev = $this->where('id','>',$id)->where('category_id',$article['category_id'])->order('id asc')->find();
		$prev = $prev?$prev->toArray():array('title'=>'返回列表','url'=>url('index/article/lists',['category_id'=>$article['category_id']]));
		$next = $next?$next->toArray():array('title'=>'返回列表','url'=>url('index/article/lists',['category_id'=>$article['category_id']]));
		$article['prev'] = array('title'=>$prev['title'],'url'=>$prev['url']);
		$article['next'] = array('title'=>$next['title'],'url'=>$next['url']);
		return $article;
	}
}