Passing the data from mysql into flutter widget Error

I have to get data from MySQL server into a flutter and pass it to widgets. but it's not working in my code. After I'm checking errors and I found some URLs are working example (//https://api.github.com/users) this URL working . but I don't know what the is the reason not working in my URL in flutter code

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart'as http;

class SudentClassView extends StatefulWidget {
@override
_SudentClassViewState createState() => _SudentClassViewState();
}

class _SudentClassViewState extends State<SudentClassView> {

Future<List> getData() async{


var url = Uri.parse('http://apitwo.studysmile.lk/apicrudphp/api/read.php');
final response = await http.get(url);
return json.decode(response.body);
}

@override
Widget build(BuildContext context) {
return Scaffold(
  appBar: AppBar(title: Text('Home Menu'),),
  body:FutureBuilder<List>(
      future: getData(),
      builder: (ctx,ss){
        if(ss.hasError)
        {
          print('error');
        }
        if(ss.hasData)
        {
          return Classes(list:ss.data);
        }
        else
        {
          return CircularProgressIndicator();
          /* Center(
            child: CircularProgressIndicator(),
          );*/
        }
      }
  ),
);
}
}

 class Classes extends StatelessWidget {
 List list;
 Classes({this.list});

 @override
 Widget build(BuildContext context) {
 return ListView.builder(
    itemCount: list == null?0:list.length,
    itemBuilder: (ctx,i){print(list.length);
      return Container(
        alignment: Alignment.center,
        margin: EdgeInsets.all(20),
        // ignore: deprecated_member_use
        child: FlatButton(
          child: Align(
              alignment: Alignment(0.2, 0.6),
              child: Text('${list[i]['name']}', style: TextStyle(fontSize: 20.0),)
          ),
          color: Color(0xff7c4dff),
          textColor: Colors.white,
          onPressed: (){print(list[i]['name']);
            //   Navigator.of(context).push(
            //     MaterialPageRoute(builder: (BuildContext context)=>StudentSubject(list:list,index:i))

            //);print("Student Class ID " + list[i]['fldStudentClassID']);
          },


        ),
      );
    }
);
}
}

This is my php code i think it's already working

<?php
header("Content-type: application/json; charset=utf-8");
require_once('db.php');
$query = 'SELECT * FROM `employee`';
$stm = $db->prepare($query);
$stm->execute();
$rows = $stm->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($rows);