stmt native

<?php
if (isset($_POST['login'])) {

$username = filter_input(INPUT_POST,'username',FILTER_SANITIZE_STRING);
$password = filter_input(INPUT_POST,'password',FILTER_SANITIZE_STRING);

  if (empty($username) || empty($password)) {
    echo "filed tidak boleh kosong";
    exit();
  }

$query = "SELECT * FROM users WHERE username=:username";
$query_params = array(
    ":username" => $username
);
try {
  $stmt = $db->prepare($query);
  $result = $stmt->execute($query_params);
}
catch (PDOException $error) {
  die("error value $error->getmessege");
}
$row = $stmt->fetch();

$login_ok = false;

if ($row) {

  $checkpassword = hash('sha256', $password . $row['salt']);
  for ($round=0; $round < 65536 ; $round++) {
    $checkpassword = hash('sha256',$checkpassword . $row['salt']);
  }
  if ($checkpassword === $row['password']) {
    $login_ok = true;
  }
}
if ($login_ok) {

unset($row['password']);
unset($row['salt']);
$_SESSION['user'] = $row['username'];
header("Location:../home");
}
else{
  echo " login gagal ";
  die();
}





}


 ?>