Why isn't the session working?

Question

PHP

Hello, I encountered sessions for the first time. Help, please, to understand why the session start does not work?

if(empty($_POST['name'])){
.....
}
else{

if(isset($_SESSION["test"])){
unset($_SESSION["test"]);
session_destroy();
}
session_start();
$_SESSION["test"] = md5(time());
header('Location: /test');
}

After redirecting to the test.php page

if(isset($_SESSION["test"])){
echo 'yes';
} else{
echo 'no';
}

Output no

Answer 1

For the session to work, it must be started on each page at the very beginning