Соедините 1 форму с 2 базами данных MySQL с PDO

Это мой первый раз здесь у меня есть вопрос, я делаю регистрационную форму, но мне нужно вставить в 2 базы данных, вот мой код.

когда я запускаю свой единственный регистр в одной базе данных, иногда db1 в другой раз db2

-Извините за мой плохой английский

-Вот регистр.php

require_once 'config/dbconfig.php';

if($user->is_loggedin()!="")
{
$user->redirect('home.php');
}

if(isset($_POST['btn-signup']))
{
$uname = trim($_POST['txt_uname']);
$umail = trim($_POST['txt_umail']);
$upass = trim($_POST['txt_upass']);
$rpass = trim($_POST['txt_rpass']);
if($uname=="") {
$error[] = "provide username !";
}
else if($umail=="") {
$error[] = "provide email id !";
}
else if(!filter_var($umail, FILTER_VALIDATE_EMAIL)) {
$error[] = 'Please enter a valid email address !';
}
else if($upass=="") {
$error[] = "provide password !";
}
else if(strlen($upass) < 6){
$error[] = "Password must be atleast 6 characters";
}

elseif($upass != $rpass){
$msg = "passwords doesn't match";
}
else
{
try
{
$stmt = $DB_con->prepare("SELECT user_name,user_email FROM users                                WHERE user_name=:uname OR user_email=:umail");
$stmt2 = $DB_con2->prepare("SELECT user_name,user_email FROM users     WHERE user_name=:uname OR user_email=:umail");
$stmt->execute(array(':uname'=>$uname, ':umail'=>$umail));
$stmt2->execute(array(':uname'=>$uname, ':umail'=>$umail));
$row=$stmt->fetch(PDO::FETCH_ASSOC);

if($row['user_name']==$uname) {
$error[] = "sorry username already taken !";
}
else if($row['user_email']==$umail) {
$error[] = "sorry email id already taken !";
}
else
{
if($user->register($fname,$lname,$uname,$umail,$upass))
{
$user->redirect('register.php?joined');
}
}
}
catch(PDOException $e)
{
echo $e->getMessage();
}
}
}

-Здесь Class.User.php

  <?php
class USER
{
private $db;

function __construct($DB_con)
{
$this->db = $DB_con;
}

public function register($fname,$lname,$uname,$umail,$upass)
{
try
{
$new_password = password_hash($upass, PASSWORD_DEFAULT);

$stmt = $this->db->prepare("INSERT INTO users(user_name,user_email,user_pass)
VALUES(:uname, :umail, :upass)");

$stmt->bindparam(":uname", $uname);
$stmt->bindparam(":umail", $umail);
$stmt->bindparam(":upass", $new_password);
$stmt->execute();

return $stmt;
}
catch(PDOException $e)
{
echo $e->getMessage();
}
}

public function login($uname,$umail,$upass)
{
try
{
$stmt = $this->db->prepare("SELECT * FROM users WHERE user_name=:uname OR user_email=:umail LIMIT 1");
$stmt->execute(array(':uname'=>$uname, ':umail'=>$umail));
$userRow=$stmt->fetch(PDO::FETCH_ASSOC);
if($stmt->rowCount() > 0)
{
if(password_verify($upass, $userRow['user_pass']))
{
$_SESSION['user_session'] = $userRow['user_id'];
return true;
}
else
{
return false;
}
}
}
catch(PDOException $e)
{
echo $e->getMessage();
}
}

public function is_loggedin()
{
if(isset($_SESSION['user_session']))
{
return true;
}
}

public function redirect($url)
{
header("Location: $url");
}

public function logout()
{
session_destroy();
unset($_SESSION['user_session']);
return true;
}
}
?>

-и DBConfig.php

 <?php
session_start();

$DB_host = "localhost";
$DB_user = "root";
$DB_pass = "";

try
{
$DB_con = new PDO("mysql:host=     {$DB_host};dbname=dblogin",$DB_user,$DB_pass);
$DB_con2 = new PDO("mysql:host=     {$DB_host};dbname=dblogin2",$DB_user,$DB_pass);
$DB_con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$DB_con2->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
echo $e->getMessage();
}include_once 'class.user.php';
$user = new USER($DB_con);
$user2 = new USER($DB_con2);