Class for BDD connection using PDO (PHP)

db.class.php

/* 
config.php
    define("DB_HOST", "localhost");
    define("DB_USER", "USER");
    define("DB_PASS", "PASSWORD");
    define("DB_NAME", "DBNAME");
*/

class Database {
    private $host = DB_HOST;
    private $user = DB_USER;
    private $pass = DB_PASS;
    private $dbname = DB_NAME;
    private $db;
    private $error;
    private $stmt;

    public function __construct() {
        $dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname . ';charset=utf8';
        $options = array(
            PDO::ATTR_PERSISTENT => true,
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ,
            PDO::ATTR_EMULATE_PREPARES => false
        );
        try {
            $this->db = new PDO($dsn, $this->user, $this->pass, $options);
        } catch (PDOException $e) {
            $this->error = $e->getMessage();
        }
    }

    public function query($query) {
        $this->stmt = $this->db->prepare($query);
    }

    public function bind($param, $value, $type = null) {
        if (is_null($type)) {
            switch (true) {
                case is_int($value):
                    $type = PDO::PARAM_INT;
                    break;
                case is_bool($value):
                    $type = PDO::PARAM_BOOL;
                    break;
                case is_null($value):
                    $type = PDO::PARAM_NULL;
                    break;
                default:
                    $type = PDO::PARAM_STR;
            }
        }
        $this->stmt->bindValue($param, $value, $type);
    }

    public function execute() {
        return $this->stmt->execute();
    }

    public function resultset() {
        $this->execute();
        return $this->stmt->fetchAll(PDO::FETCH_OBJ);
    }

    public function resultsetA() {
        $this->execute();
        return $this->stmt->fetchAll(PDO::FETCH_ASSOC);
    }

    public function column($number) {
        $this->execute();
        return $this->stmt->fetchColumn($number);
    }

    public function single() {
        $this->execute();
        return $this->stmt->fetch(PDO::FETCH_OBJ);
    }

    public function rowCount() {
        return $this->stmt->rowCount();
    }

    public function lastInsertId() {
        return $this->db->lastInsertId();
    }

    public function beginTransaction() {
        return $this->db->beginTransaction();
    }

    public function endTransaction() {
        return $this->db->commit();
    }

    public function cancelTransaction() {
        return $this->db->rollBack();
    }

    public function debugDumpParams() {
        return $this->stmt->debugDumpParams();
    }
}