codeweek/auftakt/index.php

<form action="/auftakt/" method="POST">
    <h1>Was ist 2·3</h1>
    <label>Deine Antwort:
        <input type="number" placeholder="nummer" name="number" required>
    </label>
    <button type="submit">Abgeben</button>
</form>
<?php

if (isset($_POST['number'])) {
    $number = $_POST['number'];
    if ($number === '6') {
        echo "richtig";
    } else {
        echo "falsch";
    }
}