eror

<h2 class="text-center">Edit Data Diri</h2>
<hr>

<?php
    $koneksi = new mysqli("localhost","root","","first");

 ?>



<form method="get">
    <?php $ambil=$koneksi->query("SELECT * FROM pelanggan"); ?>
    <?php $pecah=$ambil->fetch_assoc()  ?>
    <div class="form-group">
        <label>Nama</label>
        <input type="text" name="nama" class="form-control" value="<?php echo $pecah['nama']; ?>">
    </div>
    <div class="form-group">
        <label>Username</label>
        <input type="text" name="username" class="form-control" value="<?php echo $pecah['username']; ?>">
    </div>
    <div class="form-group">
        <label>Password</label>
        <input type="text" name="password" class="form-control" value="<?php echo $pecah['password']; ?>">
    </div>
    <button class="btn btn-success" name="ubah">Ubah</button>

</form>

<?php
    if (isset($_POST['ubah'])) {

            $koneksi->query("UPDATE pelanggan SET nama='$_POST[nama]', username='$_POST[username]', password='$_POST[password]' WHERE nama='$_GET[nama]'");

        echo "<script>alert('Data berhasil di ubah');</script>";
        echo "<script>location='profil.php?halaman=editprofil';</script>";
        }


?>