JSON php

<?php
 define('HOST','localhost');
 define('USER','root');
 define('PASS','');
 define('DB','absensi');

 $con = mysqli_connect(HOST,USER,PASS,DB) or die('Unable to Connect');

 ?>


<?php

 if($_SERVER['REQUEST_METHOD']=='POST'){
 //Dapatkan Data
 $username = $_POST['username'];
 $password = $_POST['password'];
 $group = $_POST['group'];

 //Membuat SQL Query
 $sql = "SELECT * FROM user WHERE username='$username' AND password='$password'";

 //memanggil file koneksi
 include 'koneksi.php';

 //exsekusi query
 $result = mysqli_query($con,$sql);

 //fetching hasil
 $check = mysqli_fetch_array($result);
 $dgroup = $check['group'];

 //jika dapatkan beberapa data
 if(isset($check) && $dgroup == $group){
 //tampilkan sukses
 echo "success";
 }else{
 //tampilkan failure
 echo "failure";
 }
 //tutup koneksi
 mysqli_close($con);
 }

 ?>