How to change the value of session - php

Question

The app.php is getting the post value from another page. And that value used for query purposes. That post value is used to edit multiple values in app.php. I post again the multiple values to edit.php to update the records that shows in app.php. What I want is when I back into app.php using <meta http-equiv="refresh" content="0;app.php" /> or <script type="text/javascript">window.history.go(-1);</script> the value in app.php should get the new or the updated value from edit.php. I'm not good using sessions. Help please?
app.php
$mysqli = new mysqli("localhost", "root", "", "app");
ob_start();
session_start()
<form name="myform" method="post" action="edit.php"/>
if (isset($_POST['submit'])) {
//unset the session value
$_SESSION['content'] = '';
$drop = $_POST['drop_1'];
$tier_two = $_POST['tier_two'];
$where = "WHERE a.app_cn='$drop' AND a.app_plan_no='$tier_two'";
$result1 = $mysqli->query(" query ");
<table>
while ($row = $result1->fetch_assoc()) {
<td><input name="checkbox[]" type="checkbox" id="checkbox[]" value="' . $row['id'] . '"'.($row['pr'] == ""?"disabled ":"").' style="cursor:pointer;" class="checkbox"></td>
}
</table>
$sPageContent = ob_get_clean();
$_SESSION['content'] = $sPageContent;
echo $_SESSION['content'];
} else {
if (isset($_SESSION['content'])) {
echo $_SESSION['content'];
}
}
</form>
Edit.php
<?php
$mysqli = new mysqli("localhost", "root", "", "app");
if (isset($_POST['submit'])) {
$counter=$_POST['counter'];
$pr=$_POST['pr'];
$pr_qty=$_POST['pr_qty'];
$N = count($counter);
for($i=0; $i < $N; $i++)
{
$result = $mysqli->query("UPDATE purchase_request SET pr='$pr[$i]', total_quantity='$pr_qty[$i]' where counter='$counter[$i]'");
}
echo'<meta http-equiv="refresh" content="0;app.php" />';
}
?>
<form class="form-horizontal" action="" method="post">
<?php
$id=$_POST['checkbox'];
$N = count($id);
for($i=0; $i < $N; $i++)
{
$result1 = $mysqli->query("
SELECT a.item_name, a.item_description, a.counter, b.counter, b.pr, b.total_quantity
FROM app a
LEFT OUTER JOIN purchase_request b
ON a.counter=b.counter
WHERE a.counter='$id[$i]'
");
while ($row = $result1->fetch_assoc())
{ ?>
<input name="item_name[]" class="textbox" type="text" value="<?php echo $row['item_name'] ?>"/>
<input name="item_description[]" class="textbox" type="text" value="<?php echo $row['item_description'] ?>"/>
<input name="pr_qty[]" id="pr_qty[]" class="textbox tb1" type="text" value="<?php echo $row['total_quantity']; ?>" />
<input name="pr[]" class="textbox" type="text" value="<?php echo $row['pr'] ?>" />
?>
<input name="submit" type="submit" id="sbtBtn" value="Update">
</form>

Answer 1

using header('Location: app.php') instead of <meta http-equiv="refresh" content="0;app.php" />
if you are using javascript to return the page it may keep the previous data. It was because our browser have the cache.
You may use
<META HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE">
and
<META HTTP-EQUIV="EXPIRES" CONTENT="Mon, 22 Jul 2002 11:12:01 GMT">
to disable the cache