Untitled

<?php
$conn = mysqli_connect("xxx", "xxx", "xxx") or die('Could not connect: ' . mysqli_connect_error());;
mysqli_select_db($conn, "xxx") or die('Could not connect: ' . mysqli_connect_error());;
?>
<html>
<head>
<title>test</title>
</head>

<body>
<form action="<?=$_SERVER['PHP_SELF'];?>" method="POST">
  <select id="Activ" name="Activ">
    <option value="1">Activ</option>
    <option value="0">Inactiv</option>
  </select>
  <input type="submit">
</form>
<?php echo $_POST['Activ'];
    mysqli_query($conn, "UPDATE useri SET Activ = '". $_POST['Activ'] ."'");
    echo "Succes!";
?>
</body>
</html>