think php5 多表查询分页 获取总数的代码方法

$data = input('get.');
    $info = [];
    //搜索条件
    if(!empty($data['title'])){
        $data['title'] = trim($data['title']);
        $info['topic_title'] = ['like','%'.$data['title'].'%'];
    }
    $list = BeModel::getList($info);
    $num = $list->total();//获取总数
    return $this->fetch('',[
        'list'  => $list,
        'title' => empty($data['title']) ? '' :$data['title'],
        'num'   => $num
    ]);

$search = [];
    $search['b.status']     = ['neq',-1];
    if(!empty($data['topic_title']) ){
        $search['b.topic_title']  =  $data['topic_title'];
    }
 
    $res = self::alias('b')->join('subject s','s.id=b.subject_id','left')
        ->join('law l','l.id=b.law_id','left')
        ->field('b.*,s.subject,l.name')
        ->where($search)
        ->order('id asc')
        ->paginate(4,false,[
        'query' => request()->param(),
        ]);
    return $res;