Update data pada form php yang sama (seperti excel)

Saya mau bikin form yang bisa nampilin data dari suatu tabel, yang mana nantinya dapat di update langsung di form tersebut, entah secara otomatis tersimpan atau dengan bantuan tombol

berikut gambaran program yg coba sy buat

Tampilan form

<form method="post" action="simpan.php" style="height: 320px; overflow: auto;">
			<table class="table-data3">

				<tr>
					<th>NIS</th>
					<th>PR</th>
					<th>Ulhar</th>
					<th>UTS</th>
					<th>UAS</th>
					<th>Total</th>
					<th>Update Nilai</th>
				</tr>

				<?php
				include 'koneksi.php';
				$data = mysqli_query($conn,"SELECT * FROM nilai");
				while($a = mysqli_fetch_array($data)){
				?>

				<tr>
					<td>
						<input type="hidden" name="id" value="<?php echo $a['id']; ?>">
						<input type="hidden" name="kd_mpl" value="<?php echo $a['kd_mapel']; ?>">
						<?php echo $a['NIS'];?>
					</td>
					<td>
						<input type="text" style="text-align: center;" name="PR" value="<?php echo $a['PR']; ?>">
					</td>
					<td>
						<input type="text" style="text-align: center;" name="Ulhar" value="<?php echo $a['Ulhar']; ?>">
					</td>
					<td>
						<input type="text" style="text-align: center;" name="UTS" value="<?php echo $a['UTS']; ?>">
					</td>
					<td>
						<input type="text" style="text-align: center;" name="UAS" value="<?php echo $a['UAS']; ?>">
					</td>
					<td>
						<input type="text" style="text-align: center;" name="total" value="<?php echo $a['total']; ?>">
					</td>
					<td>
						<input class="button2" type="submit" value="SIMPAN">
					</td>
				</tr>

				<?php } ?>

			</table>
		</form>

Syntax simpan

<?php
include 'koneksi.php';

// menangkap data yang di kirim dari form
$id = $_GET['id'];
$PR = $_GET['PR'];
$Ulhar = $_GET['Ulhar'];
$UTS = $_GET['UTS'];
$UAS = $_GET['UAS'];
$total = $_GET['total'];

// update data ke database
$result = mysqli_query($conn,"UPDATE nilai SET PR='$PR', Ulhar='$Ulhar', UTS='$UTS', UAS='$UAS', total='$total' WHERE id='$id';");

	if($result){
		echo "Data Berhasil Diubah,";
		header("location:tes_update.php");
	}
	else{
		echo ("gagal");
	}

?>

Mohon dibantu biar bisa klik update di form yang sama tanpa harus pindah form lagi, terima kasih