<?php

$db = @new mysqli('localhost', 'root', '', 'temp');

if ($db->connect_errno) {
    exit('Fehler: ' . $db->connect_error);
}

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    try {
        $sql = 'INSERT INTO test (FirstName, LastName) VALUES (?, ?)';
        $stmt = $db->prepare($sql);
        $stmt->bind_param('ss', $_POST['FirstName'], $_POST['LastName']);

        if (!$stmt->execute()) {
            throw new Exception($db->error);
        } else {
            echo '<p>Eintrag erfolgreich!</p>';
        }
    }
    catch (Exception $e) {
        exit($e -> getMessage());
    }
}

?>

<form action="" method="post">
    Vorname: <input type="text" name="FirstName" /><br />
    Nachname: <input type="text" name="LastName" /><br />
    <input type="submit" value="Speichern" />
</form>