public function Register($CONN, $iFirstName, $iLastName, $iUsername, $iEmailAddress, $iPassword, $iCountry, $iCity)
{

  $SubmitOK = '1';
  $Core = new Core();
  $iPassword = password_hash($iPassword, PASSWORD_DEFAULT);
  $Core->CheckForEmpty(array('iFirstName', 'iLastName', 'iUsername', 'iEmailAddress', 'iPassword', 'iCountry'), 'index.php');


  if($SubmitOK == '1') {
    try {
      $SQL = 'INSERT INTO Users (FirstName, LastName, Username, Password, EmailAddress, City, Country) VALUES (:iFirstName, :iLastName, :iUsername, :iPassword, :iEmailAddress, :iCity, :iCountry)';
      $SQL = $CONN->prepare($SQL);
      $SQL->execute(array("iFirstName" => $iFirstName, "iLastName" => $iLastName, "iUsername" => $iUsername, "iPassword" => $iPassword, "iEmailAddress" => $iEmailAddress, "iCity" => $iCity, "iCountry" => $iCountry));
      $_SESSION['Success'] = 'Uspesno ste se registrovali';
      header('location: index.php');
      exit();
    } catch(PDOException $e) {
       echo "Error: " . $e->getMessage();
    }
  } else {
      $_SESSION['Error'] = 'Doslo je do greske! Molimo vas pokusajte ponovo';
      header('location: index.php');
      exit();
  }
}

<?php
  session_start();
  include 'includes.php';



  if($_SERVER['REQUEST_METHOD'] === 'POST') {
    $iFirstName = htmlspecialchars($_POST['iFirstName']);
    $iLastName = htmlspecialchars($_POST['iLastName']);
    $iPassword = $_POST['iPassword'];
    $iEmailAddress = htmlspecialchars($_POST['iEmailAddress']);
    $iUsername = htmlspecialchars($_POST['iUsername']);
    $iCountry = $_POST['iCountry'];
    $iCity = htmlspecialchars($_POST['iCity']);


    $User->Register($CONN, $iFirstName, $iLastName, $iUsername, $iEmailAddress, $iPassword, $iCountry, $iCity);
  }
  $Smarty->assign('Title', 'Home');
  $Smarty->assign('Message', $Core->GetMessage());
  $Smarty->display('header.tpl');

  $News = $Core->GetNews();
  $Important = $Core->GetImportant();
  $Smarty->assign('News', $News);
    $Smarty->assign('Important', $Important);
  $Smarty->display('index.tpl');
  $Smarty->display('footer.tpl');

?>