Updating PHP shows double data where it shouldn't - php

Question

So me and my group of students are making a web application for a company. On this page we're trying to show different startup companies with different group numbers. We'd also want to have the option to update this number. The update part works fine and it shows the right group number behind someone his/her name. The real problem here is, if I update one of the different group numbers and reload the page, all of the groups have the same number as shown on the webpage, but in the database it shows the correct number that i've updated.
So I would like to have the right update number shown right away. This is my php code down below.
<?php
session_start();
require 'header.php'; //
require 'includes/dbh.inc.php';
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$update = mysqli_real_escape_string($conn, $_POST['group']);
$sql = "SELECT user_uid, user_name, group_id, active FROM groups";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while ($row = $result->fetch_assoc()) {
if(!isset($_POST['groupnumber'])) {
$gnum = $row['group_id'];
}
else {
$gnum = $update;
}
echo "<br> Name : " . $row["user_name"] . " - Group number:" . $gnum . "<br> Select new group" .
"<form method='post'>
<input type='text' name='group'>
<button name='groupnumber' value='". $row['user_uid'] ."'> Update </button>
</form>". "<br>";
}
} else {
echo "0 results";
}
if(isset($_POST['groupnumber'])){//if the submit button is clicked
$id = mysqli_real_escape_string($conn, $_POST['groupnumber']);
$update = mysqli_real_escape_string($conn, $_POST['group']);
$query="UPDATE groups SET group_id='$update' where user_uid = $id";
$conn->query($query) or die("Cannot update");//update or error
}
$conn->close();
?>
Sorry if it's kinda messy, I'm still a student and i'm just a basic PHP guy :)

Answer 1

Of course it does, that's what you have in your while-loop, here:
if(!isset($_POST['groupnumber'])) {
$gnum = $row['group_id'];
}
else {
// On a POST always show the posted value for all groups
$gnum = $update;
}