function update_user() {
		global $connection;
		$username = $_POST['username'];
		$password = $_POST['password'];
		$id = $_POST['id'];
		echo $id;
		if (!$connection) {
			die ('connection failed');
		};
		$query = "UPDATE users SET ";
		$query .= "username = '$username', ";
		$query .= "password = '$password' ";
		$query .= "WHERE id = $id ";

		$result = mysqli_query($connection, $query);
		if (!$result) {
			die('query failed' . mysqli_error($connection));
		};

	}