Toy Messages classes

Message.php

<?php

class Message
{
    public function __construct($msg, $user) {
        $this->msg = $msg;
        $this->user = $user;
        $this->created = new DateTime();
    }

    public function getAsHtml() {
        $html = "<li>" . $this->user . " said: ";
        $html .= "<em>" . $this->msg . "</em>";
        $datetime = $this->created;
        $html .= " on " . $datetime->format('F jS');
        $html .= "</li>";
        return $html;
    }

}

messages.php

<?php
session_start();
require('Message.php');
?>

<h1>Messages</h1>

<a href="new_message.php">New message</a>

<?php

if($_SESSION['messages'] && is_array($_SESSION['messages'])) {
    echo "<ul>";
    foreach($_SESSION['messages'] as $msg) {
        $data = unserialize($msg);
        echo $data->getAsHtml();
    }
}

new_message.php

<?php
session_start();
require('Message.php');

if($_POST) {
    $user    = filter_input(INPUT_POST, "name", FILTER_SANITIZE_STRING);
    $msg     = filter_input(INPUT_POST, "message", FILTER_SANITIZE_STRING);
    if(!empty($msg)) {
        $message = new Message($msg, $user);
        $_SESSION['messages'][] = serialize($message);
        
        header("Location: messages.php");
    } else {
        echo "Try again";
    }
}
?>

<h1>New Message</h1>

<form method="post">
Name: <input type="text" name="name" />
Message: <textarea name="message"></textarea>
<input type="submit" value="save" />
</form>