Error Notice: Undefined index: keyword in D:\xampp\htdocs\web_bapa\web\ajax\mytable.php on line 4
Kenapa ya saya mau pakai live search ajax tapi malah error ini code nya : 

ajax/mytable.php
<?php

include '../functions/fungsi.php';

$keyword = $_GET["keyword"];
// $query = "SELECT * FROM tb_login WHERE username LIKE '%$keyword%'";
$query = query("SELECT * FROM tb_login WHERE username LIKE '%$keyword%'");
?>
<table class="table table-sm table-bordered" style="background-color: #dadfe1;  border-radius: 10px;">
<thead>

<tr class="text-center">
        <th>No</th>
        <th>Username</th>
        <th>Password</th>
        <th>Jenis</th>
        <th colspan="2">Lainnya</th>
    </tr>
</thead>
<?php

$no = 1;
foreach($query as $r){
?>
  <tbody>
    <tr class="text-center">
      <td><?= $no ?></td>
      <td><?= $r['username']?></td>
      <td><?= $r['password']?></td>
      <td><?= $r['level']?></td>
      <td><a class="edit" href="admin.php?&edit&id=<?= $r['id'] ?>">Edit</a></td>
      <td><a class="hapus">hapus</a></td>
    </tr>
  </tbody>
<?php

$no++;
}

?>
</table>
dan ini js/script.js :

//ambil elemen yang dibutuhkan
let keyword = document.getElementById('keyword');
let tombolcari = document.getElementById('tombol-cari');
let container = document.getElementById('container');

//tambahkan event ketika ditulis
keyword.addEventListener('keyup', function(){
//buat objek abjad
let xhr = new XMLHttpRequest();

//cek kesiapan ajax
xhr.onreadystatechange = function(){
if (xhr.readyState == 4 && xhr.status == 200) {
container[removed] = xhr.responseText;
}
}

//eksekusi ajax
xhr.open('GET', '../ajax/mytable.php?keyword=' + keyword.value, true);
xhr.send();
});

Gimana ya mohon pencerahannya