PHP OOP Class Database

class database extends PDO{
    private $host = DB_HOST;
    private $user = DB_USER;
    private $pass = DB_PASS;
    private $dbname = DB_NAME;
    private $dbh;
    private $error;
    private $stmt;

    public function __construct()
    {
        // Set DSN
        $dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname;

        // Set options
        $options = array(
            PDO::ATTR_PERSISTENT => true,
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
        );

        try {
            $this->dbh = new PDO($dsn, $this->user, $this->pass, $options);
        }// Catch any errors
        catch (PDOException $e) {
            return $this->error = $e->getMessage();
        }
    }

    public function classConnectTest()
    {
        return "Connected";
    }

    public function query($query){
        $this->stmt = $this->dbh->prepare($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 mutltiply(){
        $this->execute();
        return $this->stmt->fetchAll(PDO::FETCH_ASSOC);
    }

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

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

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

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

    public function endTransaction(){
        return $this->dbh->commit();
    }
    public function cancelTransaction(){
        return $this->dbh->rollBack();
    }

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



}