how to get data from mysql and save it in a variable without using listview builder or future builder

Question

i am totally new to flutter and even coding so kindly help me and also put it in simple terms here is my model class

import 'dart:convert';

class LoginUserDataModel {
  LoginUserDataModel({
    required this.id,
    required this.name,
    required this.email,
    required this.phoneNumber,
    required this.password,
    required this.address,
  });

  String id;
  String name;
  String email;
  String phoneNumber;
  String password;
  String address;

  factory LoginUserDataModel.fromJson(Map<String, dynamic> json) =>
      LoginUserDataModel(
        id: json["id"],
        name: json["name"],
        email: json["email"],
        phoneNumber: json["phone_number"],
        password: json["password"],
        address: json["address"],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "email": email,
        "phone_number": phoneNumber,
        "password": password,
        "address": address,
      };
}

I post the phone_number to php which intern gives me the row which has that variable and then i get in using the model class. i can see the json data when i print it but i want to save individual value in variables so i can use it later on

here is my post request where i post the phone number to php which gives me the row containig that phone number

Future loginWithMobile(String isoCode, String mobileNumber) async {
    var url = 'http://192.168.1.5/server/login.php';
    var data = {
      "phone_number": mobileNumber,
    };

    http.Response res = await http.post(Uri.parse(url), body: data);
    var details = json.decode(json.encode(res.body));
}