$host = 'localhost';
$db   = 'cssnewlogin';
$user = 'root';
$pass = '';
$charset = 'utf8';

//We do the connection:
$dsn = "mysql:host=$host;dbname=$db;charset=$charset";
$opt = [
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES   => false,
];
$pdo = new PDO($dsn, $user, $pass, $opt);
$pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, FALSE);

$sthinsert = $pdo->prepare(

    "INSERT INTO lithuania_customers_2016

    (user_id, customer_db_id, campaign_id)

    VALUES (:user_id, :customer_db_id, :campaign_id)"

    );

    $sthinsert->bindValue(':user_id', $user_id, PDO::PARAM_INT);
    $sthinsert->bindValue(':customer_db_id', $customer_db_id, PDO::PARAM_INT);
    $sthinsert->bindValue(':campaign_id', $campaign_id, PDO::PARAM_INT);

$sthinsert->execute();