PHP: compare input string with random string

I am learning PHP and trying to compare a random string with a input from a user.

I have this code for the random string:

$rand = substr(uniqid('', true), -5);
$_SESSION['random'] = $rand;

and this code prints the random string.

<?php echo $_SESSION['random']; ?>

This is the input from the user:

<input type="text" placeholder="Typ string" name="rand" required>

I am now trying to compare the random string with the input from the user:

if (isset($_POST['rand']) and $_POST['rand'] !='') {
if ($_SESSION['random'] == $_POST['rand']) {
   Do some stuff;
}}

Can someone please help me with this?