$orderno =$_POST['order_no'][$i];
$status =$_POST['order_status'][$i];

<?php
if(isset($_POST['order_status']))
{
$dbhost = 'localhost';
$dbuser = 'root';
$dbpass = '';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
die('Could not connect: ' . mysql_error());
}
$orderno =$_POST['order_no'][$i];
$status =$_POST['order_status'][$i];
print_r($_POST['order_no']);
$sql = 'UPDATE Orders SET status="' . '$status'. '" WHERE   Orderno="' .'$orderno' . '"';
echo $sql;
mysql_select_db('PurchaseOrders');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
die('Could not update data: ' . mysql_error());
}
echo "Updated data successfullyn";
mysql_close($conn);
}
?>

$sql = 'UPDATE Orders SET status="' . $status. '" WHERE   Orderno="' .$orderno . '"';

$sql = "UPDATE Orders SET status='" . $status . "' WHERE   Orderno= '" . $orderno . "' ";

$sql = "UPDATE Orders SET status='$status' WHERE  Orderno='$orderno'";