后台报错

@@ -47,6 +47,8 @@ class SchoolController extends AdminBaseController{
         $id = $this -> request -> param();
         $data = Db::name('school') -> where('id',$id['ids']) -> find();
         $data_grade = Db::name('grade_class') -> where('school_id',$id['ids']) -> select();
+        $grade_id = [];
+        $grade_class = [];
         foreach ($data_grade as $key => $val){
             $grade_id[] = $val['id'];
             $grade_class[] = $val['grade'].','.$val['class'];