Untitled

<?php
include("config.php');
session_start();
?>
<html>
<head>
<link rel="stylesheet" href="index.css" type="text/css">
</head>
<body>
<center>
<form method="post" action="">
    Gebruikersnaam: <input type="text" name="1"><br>
    Wachtwoord: <input type="password" name="2"><br>
    <input type="submit" name="submit" value="Registreer!">
</form>
</center>
<?php
    if (isset($_POST["submit"])) {
        $one = $_POST["1"];
        $two = $_POST["2"];
        $a = $db->prepare("INSERT INTO Users SET Username=?, Password=?");
        $a->execute(array($one, $two));
        if ($a) {
            echo "<script>alert('Gelukt!');</script>";
$_SESSION['Users'] = $one;
        } else {
            echo "<script>alert('Niet gelukt!');</script>";
        }
    }
?>
</body>
</html>