class User extends Database
{

    public function data($userid)
    {
        $getRow = $this->getConnect()->getRow("SELECT * FROM users WHERE userid = ?", [$userid]);

        return $getRow;
    }

}

class Database
{

    private $dbh = NULL;
    private $instance = NULL;

    public function __construct($username = 'root', $password = '', $host = '127.0.0.1', $dbname = 'testdb', $options = [])
    {
        try  {
            $this->dbh = new PDO("mysql:dbname={$dbname};host={$host};charset=utf8", $username, $password);
            $this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->dbh->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
        } catch (PDOException $ex) {
            throw new Exception($ex->getMessage());
        }

    }

    public function getConnect()
    {
        if($this->instance == NULL)
        {
            $this->instance = new self();
        }
        return $this->instance;
    }
}