Undefined index

boa tarde alguém me ajuda...

Notice: Undefined index: id in C:\xampp\htdocs\novosite\entrar\atualizarregistro.php on line 67

atualizarregistro.php

 <?php

	if(!isset($_GET['funcao'])=="editar"){

$con = mysqli_connect("localhost", "root", "", "acheiteste");

	$selectid = $_GET['id'];

	$sql = "SELECT * FROM clientes WHERE id = '$selectid'";
	$sql2 = mysqli_query($con, $sql);
	while($ln = mysqli_fetch_array($sql2)){
?>
 <form method="post" name="form1" action="atualizar.php?funcao=editar&id=<?=$ln['id']?>">
 <table align="center">
 <tr valign="baseline">
 <td nowrap align="right">Cli_nome:</td>
 <td><input type="text" name="nome" value="<?=$ln['nome']?>" size="32"></td>
 </tr>
 <tr valign="baseline">
 <td nowrap align="right">Cli_email:</td>
 <td><input type="text" name="email" value="<?=$ln['email']?>" size="32"></td>
 </tr>
 <tr valign="baseline">
 <td nowrap align="right">Cli_senha:</td>
 <td><input type="text" name="senha" value="<?=$ln['senha']?>" size="32"></td>
 </tr>
 <tr valign="baseline">
 <td nowrap align="right"> </td>
 <td><input type="submit" value="Atualizar registro"></td>
 </tr>
 </table>
 <input type="hidden" name="MM_update" value="form1">
 <input type="hidden" name="id" value="">
 </form>
 <p> </p>
 </div>
</div></div>
<?php
	}}// Fehca Loop
?>

atualizar.php

<?php
$con = mysqli_connect("localhost", "root", "", "acheiteste");

$postnome = $_POST['nome'];
$postemail = $_POST['email'];
$postsenha = $_POST['senha'];
$getid = $_GET['id'];

 if($_GET['funcao']=="editar"){

$sql = "UPDATE clientes SET nome = '$postnome', email = '$postemail',
 senha = '$postsenha'
WHERE id = '$getid'
";

mysqli_query($con, $sql);

 echo "<meta http-equiv='refresh' content='0; URL= pagina-segura.php'>

<script type=\"text/javascript\">
alert(\"Alterado com Sucesso!\");
</script>

 ";
 }
?>