PHP 换星星

//订单详情
    public function details(){
        $id = I('get.id');
        $comm = $this->getInstance();
        $res = $comm->select_view(1,0,'orders');
        $res = $res['list'][0];
        $needRep = array(
            'username','address','mobile','expressno'
        );
        foreach($res as $key => $row){
            if(in_array($key,$needRep)){
                if($row){
                    $need = $this->repStar($row,"utf-8");
                    $res[$key] = $need;
                }
            }
        }
        $this->assign('data',$res);
        $this->display();
    }
    //换星星
    private function repStar($str,$encoding = "utf-8"){
        $len = mb_strlen($str,$encoding);
        //判断是否大于2
        $need = null;
        if(!$len){
            return false;
        }
        if($len>1){
            if($len%2 !=0){
                $len -= 1;
            }
            $need = mb_substr($str,0,$len/2,$encoding);
            $star = $this->getStar($len/2+1);
            $need .= $star;
        }else{
            $need = "*";
        }
        return $need;
    }
    //生成需要的星星
    private function getStar($nun){
        $reVal = null;
        if($nun){
            for($i = 0; $i < $nun; $i++){
                $reVal .= "*";
            }
            return $reVal;
        }else{
            return false;
        }

    }