php上下级获取方法

php上下级获取方法，摘抄自某源码，保存下来方便学习下

//获取上级会员
public function parent_user($uid,$num=1,$lv=1)
{
    $pid = db($this->table)->where('id',$uid)->value('parent_id');
    $uinfo = db($this->table)->where('id',$pid)->find();
    if($uinfo){
        if($uinfo['parent_id']&&$num>1) $data = self::parent_user($uinfo['id'],$num-1,$lv+1);
        $data[] = ['id'=>$uinfo['id'],'pid'=>$uinfo['parent_id'],'lv'=>$lv,'status'=>$uinfo['status']];
        return $data;
    }
    return false;
}


//获取下级会员
public function child_user($uid,$num=1,$lv=1)
{

    $data=[];
    $where = [];
    if ($num ==1) {
        $where[] = ['parent_id','=',$uid];
        $data = db('xy_users')->where('parent_id', $uid)->field('id')->column('id');

    }else if ($num == 2) {
        //二代
        $ids1 = db('xy_users')->where('parent_id', $uid)->field('id')->column('id');
        $ids1 ? $where[] = ['parent_id','in',$ids1] : $where[] = ['parent_id','in',[-1]];
        $data = db('xy_users')->where($where)->field('id')->column('id');
        $data = $lv ? array_merge($ids1 ,$data) : $data;
    }else if ($num == 3) {
        //三代

        $ids1 = db('xy_users')->where('parent_id', $uid)->field('id')->column('id');
        $ids1 ? $wher[] =  ['parent_id','in',$ids1] : $wher[] =  ['parent_id','in',[-1]];
        $ids2 = db('xy_users')->where($wher)->field('id')->column('id');
        $ids2 ? $where[] = ['parent_id','in',$ids2] : $where[] = ['parent_id','in',[-1]];
        $data = db('xy_users')->where($where)->field('id')->column('id');
        $data = $lv ? array_merge($ids1 ,$ids2, $data) : $data;
    }else if ($num == 4) {
        //四带
        $ids1 = db('xy_users')->where('parent_id', $uid)->field('id')->column('id');
        $ids1 ? $wher[] =  ['parent_id','in',$ids1] : $wher[] =['parent_id','in',[-1]];
        $ids2 = db('xy_users')->where($wher)->field('id')->column('id');
        $ids2 ? $where2[] = ['parent_id','in',$ids2] : $where2[] = ['parent_id','in',[-1]];
        $ids3 = db('xy_users')->where($where2)->field('id')->column('id');
        $ids3 ? $where[] = ['parent_id','in',$ids3] : $where[] = ['parent_id','in',[-1]];
        $data = db('xy_users')->where($where)->field('id')->column('id');
        $data = $lv ? array_merge($ids1 ,$ids2,$ids3, $data): $data;

    }else if ($num == 5) {
        //五带
        $ids1 = db('xy_users')->where('parent_id', $uid)->field('id')->column('id');
        $ids1 ? $wher[] =  ['parent_id','in',$ids1] : $wher[] =  ['parent_id','in',[-1]];
        $ids2 = db('xy_users')->where($wher)->field('id')->column('id');
        $ids2 ? $where2[] = ['parent_id','in',$ids2] : $where2[] = ['parent_id','in',[-1]];
        $ids3 = db('xy_users')->where($where2)->field('id')->column('id');
        $ids3 ? $where3[] = ['parent_id','in',$ids3] : $where3[] = ['parent_id','in',[-1]];
        $ids4 = db('xy_users')->where($where3)->field('id')->column('id');
        $ids4 ? $where[] = ['parent_id','in',$ids4] : $where[] = ['parent_id','in',[-1]];
        $data = db('xy_users')->where($where)->field('id')->column('id');

        $data = $lv ? array_merge($ids1 ,$ids2,$ids3,$ids4, $data) :$data;
    }

    return $data;
}