How can I update echo $_SESSION['balance'] in real time when I make changes into the database?

How can I update echo $_SESSION['balance'] in real time when i make changes into the database? I am trying to build a send and recieve system but when i send an ammount it doesnt get updated in real time.. How can i acheve that?

<?php
session_start();
include "db_conn.php";
if (!$conn) {
	echo "Connection failed!";
}
$a = $_SESSION['id'];
$b = $_SESSION['balance'];
$c = $_REQUEST['amount'];
$sql = "UPDATE users SET balance=balance - ($c) WHERE id=($a)";
if ($conn->query($sql) === TRUE) {
  echo "Record updated successfully";
} else {
  echo "Error updating record: " . $conn->error;
}

 ?>