thinkphp-butter/app/service/ProductClassService.php

<?php

namespace app\service;

use app\model\ProductClass;
use think\db\exception\DataNotFoundException;
use think\db\exception\DbException;
use think\db\exception\ModelNotFoundException;
use think\Model;

class ProductClassService{
    /**
     * @throws ModelNotFoundException
     * @throws DataNotFoundException
     * @throws DbException
     */
    public static function getProductClassById($id){
        $del_flag = "N";
      return  (new \app\model\ProductClass)
          //->field('')
          ->where("type_id",$id)
          ->where("del_flag",'=', "N")
          ->select();
    }

    public static function getProductClass(){

        $type_data =  (new ProductClass)->field("type_id")->group("type_id")->select();
        for ($i=0;$i<count($type_data);$i++){

            $type_data[$i]["data"]=(new ProductClass)
                ->field('id, parent_name, parent_id, name')
                ->where('type_id', $type_data[$i]['type_id'])
                ->select();
            for ($j=0;$j<count($type_data[$i]["data"]);$j++){
                //$type_data[$i]["data"][$j]["data"] = [];
                $type_data[$i]["data"][$j]["data"]=(new ProductClass)
                    ->field('parent_name, parent_id, name')
                    ->where('parent_id', $type_data[$i]['data'][$j]['parent_id'])

                    ->select();
            }
        }

        return $type_data;
    }

}