<?php
@session_start();
$_session['count']= $_GET['count'];
$_session['sum']= $_GET['Sum'];
for ($i=0;$i<$_session['count'];$i++){
//make necessary changes here as well
echo unserialize($_GET['serialized_name'])[$i];
//use session to store your data from previous page
?>
<?php
//put this code above the form to process the submitted data which was previously sent to update.php
if(isset($_POST[submit])){
//Your code
e.g.
$name=$_POST['name']
//whenever you want to access previous data just get it from session variable.
e.g. $count=$_SESSION['count'];
}?>
<html>
<!--Submit the data of the form to itself instead of update.php -->
<form method="post" action="<?php echo $PHP_SELF;?>">
<!--your html code -->
</form>
</html>