<?php
session_start();
include 'Token.php';
?>
<form method="post">
    <div><input type="text" name="number"></div>
    <input type="hidden" name="token" value="<?= Token::create() ?>"/>
    <div><input type="submit" name="submit"></div>
</form>
<?php
echo $_SESSION['token'];
if(isset($_POST['submit']) && Token::check()) {
    echo "<br>OK";
}
?>