Gagal mengambil data dari kode otomatis

permisi master, lgi nemu bug nih, jdi sya lgi coba2 ngulik php,, sya nemu cara bikin kode otomatis,, datanya udah berasil disimpan & ditampilin, nah masalahnya pas mau diedit mlah ada bug,, kode yang ditampilin di textbox sma yang di urlnya beda,, kyak gni gan

ngatasinnya gmana ya master.. ini kodenya form editnya

<?php
require_once "kode_auto.php";

	if(isset($_GET['kd_buku'])){
		$kode_otomatis = $_GET['kd_buku'];
	}

	$tampil = "SELECT * FROM buku WHERE kd_buku='$kode_otomatis'";
	$query = mysqli_query($koneksi, $tampil);
	$data = mysqli_fetch_array($query);

	$error = "";
	if(isset($_POST['edit'])){
		$kode_otomatis = $_POST['kd_buku'];
		$nama_buku = $_POST['nama_buku'];
		$tgl_pinjam = $_POST['tgl_pinjam'];
		$tgl_kembali = $_POST['tgl_kembali'];
		$thn_terbit = $_POST['thn_terbit'];
		$jns_buku = $_POST['jns_buku'];

		$edit = "UPDATE buku SET nama_buku='$nama_buku',tgl_pinjam='$tgl_pinjam',tgl_kembali='$tgl_kembali',thn_terbit='$thn_terbit',jns_buku='$jns_buku' WHERE kd_buku='$kode_otomatis'";
		$query2 = mysqli_query($koneksi, $edit);
		if($query2){
			header('location: index.php');
		}else{
			echo $error = "gagal mengedit data";
		}
	}

?>
// form edit
<form action="" method="POST" enctype="multipart/form-data">
			<table width="50%">
				<tr>
					<td>Kode Buku</td>
					<td><input type="text" name="kode_otomatis" size="5" value="<?= $kode_otomatis; ?>" disabled=""></td>
				</tr>
				<tr>
					<td>Nama Buku</td>
					<td><input type="text" name="nama_buku" value="<?= $data['nama_buku'];?>" size="20"></td>
				</tr>
				<tr>
					<td>Tanggal Pinjam</td>
					<td><input type="text" name="tgl_pinjam" class="tanggal" value="<?= $data['tgl_pinjam'];?>" size="10"></td>
				</tr>
				<tr>
					<td>Tanggal Kembali</td>
					<td><input type="text" name="tgl_kembali" class="tanggal" value="<?= $data['tgl_kembali'];?>" size="10"></td>
				</tr>
				<tr>
					<td>Tahun Terbit</td>
					<td>
						<select name="thn_terbit" id="">
							<option value="2000" <?php if($data['thn_terbit']=="2000"){ echo "selected";}?>>2000</option>
							<option value="2001" <?php if($data['thn_terbit']=="2001"){ echo "selected";}?>>2001</option>
							<option value="2002" <?php if($data['thn_terbit']=="2002"){ echo "selected";}?>>2002</option>
							<option value="2003" <?php if($data['thn_terbit']=="2003"){ echo "selected";}?>>2003</option>
							<option value="2004" <?php if($data['thn_terbit']=="2004"){ echo "selected";}?>>2004</option>
							<option value="2005" <?php if($data['thn_terbit']=="2005"){ echo "selected";}?>>2005</option>
							<option value="2006" <?php if($data['thn_terbit']=="2006"){ echo "selected";}?>>2006</option>
							<option value="2007" <?php if($data['thn_terbit']=="2007"){ echo "selected";}?>>2007</option>
							<option value="2008" <?php if($data['thn_terbit']=="2008"){ echo "selected";}?>>2008</option>
						</select>
					</td>
				</tr>
				<tr>
					<td>Jenis Buku</td>
					<td>
						<input type="radio" name="jns_buku" value="Majalah Anak" <?php if($data['jns_buku']=="Majalah Anak"){ echo "checked"; }?>>Majalah Anak
						<input type="radio" name="jns_buku" value="Novel" <?php if($data['jns_buku']=="Novel"){ echo "checked"; }?>>Novel
						<input type="radio" name="jns_buku" value="Tabloid" <?php if($data['jns_buku']=="Tabloid"){ echo "checked"; }?>>Tabloid
					</td>
				</tr>
				<tr>
					<td colspan="2"><?= $error;?></td>
				</tr>
				<tr>
					<td> </td>
					<td>
						<input type="submit" name="edit" value="SIMPAN">
						<input type="submit" name="batal" value="BATAL">
					</td>
				</tr>
			</table>
		</form>

mohon bantuannya master