Loggin session not working in another page - php

Question

I have a page name authentication.php once licked login it will show the session information in the same page, but when i try to display the same logged user information in another page like userprofile.php it won't show anything
<?php
if ($_POST) {
$logdb = new PDO('mysql:host=localhost;dbname=mydbname', 'root', '12345');
$logdb->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $logdb->prepare("SELECT * FROM users WHERE username=:username AND password=:password");
$stmt->bindParam(":username", $_POST['username']);
$stmt->bindParam(":password", $_POST['password']);
$stmt->execute();
$atributes = $stmt->fetch(PDO::FETCH_OBJ);
if ($atributes) {
session_start();
//$_SESSION["loggedIn"] = true;
$_SESSION['username'] = $_POST['username'];
$_SESSION["ID"] = $atributes->ID;
$_SESSION["country"] = $atributes->country;
} else {
echo 'Login failed!';
}
} else {
echo '<form name="login" action="" method="POST">
Username: <br />
<input type="text" name="username"/><br />
Password: <br />
<input type="password" name="password"/><br />
<button type="submit">Login</button>
Register</form>';
}
?>
<?php
echo ($_SESSION["ID"]);
echo ($_SESSION["username"]);
echo $atributes->country;
?>
Here is what i use in a new page to display logged user information but am not getting any result and also no error please can you assist me on that?
<?php
session_start();
if(!isset($_SESSION['username'])) {
$_SESSION["ID"] = $atributes->ID;
$_SESSION["username"] = $atributes->username;
$_SESSION["country"] = $atributes->country;
} ?>
<?php
echo ($_SESSION["ID"]);
echo ($_SESSION["username"]);
echo $atributes->country;
?>
Also at the header of my page i have a navbar like this
<?php if(!isset($_SESSION['username'])) {
include($root . 'includings/unloggedU.php');
}else{
include($root . 'includings/loggedU.php');
} ?>

Answer 1

On the first page set $_SESSION['country'] = $atributes->country; as there is currently no session variable set for that in your code.
And on the second page you should have access to all of the session variables - which you can test individually to see if they are set if you want to.
<?php
session_start(); // always put this at the top of the page see Ryan's comments
echo $_SESSION["ID"] . "<br />";
echo $_SESSION["username"] . "<br />";
echo $_SESSION["country"] . "<br />";
?>