Can't get session variable to work in sql UPDATE statement - php

Question

First page:
<?php
session_start();
//db info
$conn = new mysqli("$server","$user_name","$password","$database");
$sql = "SELECT id FROM Client_Information order by id desc limit 1";
$result = $conn->query($sql);
if ($result->num_rows >0) {
while($row = $result->fetch_assoc()) {
$id=$row['id'] + 1;
}
}
$_SESSION['id'] = $id;
$sitename = $_POST['sitename'];
$sitetype = $_POST['sitetype'];
$color1 = $_POST['color1'];
$color2 = $_POST['color2'];
$color3 = $_POST['color3'];
$color4 = $_POST['color4'];
$sitedescription = $_POST['sitedescription'];
$aboutme = $_POST['aboutme'];
$contactname = $_POST['contactname'];
$phone = $_POST['phone'];
$email = $_POST['email'];
$address = $_POST['address'];
if (isset($sitename) && isset($sitetype) && isset($color1)
&& isset($color2) && isset($contactname) && isset($phone)
&& isset($email) && isset($address) && isset($sitedescription)
&& isset($aboutme)) {
$sql = "INSERT INTO Client_Information (id, sitename, sitetype, color1, color2,
color3, color4, sitedescription, aboutme,
contactname, phone, email, address, timestamp)
VALUES ('$id', '$sitename', '$sitetype', '$color1', '$color2',
'$color3', '$color4', '$sitedescription', '$aboutme',
'$contactname', '$phone', '$email', '$address',
CURRENT_TIMESTAMP)";
$conn->query($sql);
header('Location: images.php');
}
mysqli_close($conn);
?>
Second page:
<?php
session_start();
echo $_SESSION['id'];
//db info
$conn = new mysqli("$server","$user_name","$password","$database");
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
$wherevar = $_SESSION['id'];
$exsitename1 = $_POST['exsitename1'];
$exsitename2 = $_POST['exsitename2'];
$exsitename3 = $_POST['exsitename3'];
$exsitename4 = $_POST['exsitename4'];
$exsiteurl1 = $_POST['exsiteurl1'];
$exsiteurl2 = $_POST['exsiteurl2'];
$exsiteurl3 = $_POST['exsiteurl3'];
$exsiteurl4 = $_POST['exsiteurl4'];
$exsitedescr1 = $_POST['exsitedescr1'];
$exsitedescr2 = $_POST['exsitedescr2'];
$exsitedescr3 = $_POST['exsitedescr3'];
$exsitedescr4 = $_POST['exsitedescr4'];
if (isset($exsitename1) && isset($exsitename2) && isset($exsitename3) && isset($exsitename4)
&& isset($exsiteurl1) && isset($exsiteurl2) && isset($exsiteurl3) && isset($exsiteurl4)
&& isset($exsitedescr1) && isset($exsitedescr2) && isset($exsitedescr3) && isset($exsitedescr4)) {
$sql = "UPDATE Client_Information
SET exsitename1='$exsitename1', exsitename2='$exsitename2', exsitename3='$exsitename3',
exsitename4='$exsitename4', exsiteurl1='$exsiteurl1', exsiteurl2='$exsiteurl2',
exsiteurl3='$exsiteurl3', exsiteurl4='$exsiteurl4', exsitedescr1='$exsitedescr1',
exsitedescr2='$exsitedescr2', exsitedescr3='$exsitedescr3', exsitedescr4='$exsitedescr4'
WHERE id = '$wherevar'";
$conn->query($sql);
header('Location: index.php');
}
session_destroy();
mysqli_close($conn);
?>
So the first page works fine and inserts all the data into the db, but when the second page is ran, it doesn't update the same row that was inserted on the first page. It just leaves all those variable.
On the second page, I'm trying to have it edit the row that was just created.