if(isset($_POST['submit'])){
  $username = $_POST['username'];
  $password = $_POST['password'];
  $nickname = $_POST['nickname'];
  $email = $_POST['email'];

  // print Command working here..

  // Function start. this function is not working no.
  create_user($conn, $username, $password, $nickname, $email);
  header('location: index.php?All=Users');
  exit();

  }

  // Function. Include
  function create_user($conn, $username, $password, $nickname, $email){
    $timestamp = date('Y-m-d H:i:s');
    $user_ip = getUserIp();

    $sql = "INSERT INTO `users` (`user_id`, `user_login`, `user_pass`, `user_nickname`, `user_email`, `user_status`, `timestamp`, `user_ip`)
    VALUES ('', '$username', '$password', '$nickname', '$email', '0', '$timestamp', '$user_ip')";
    $conn->query($sql) === TRUE;
}