Database connection doesn't work

Hoi allemal,

Ik ben nieuw in OOP.
Ik heb zo juist mijn eerste OOP code geschreven maar hij werkt niet.
Kunnen jullie aub naar mijn code kijken en de fout aanwijzen?

Alvast bedankt



<?php

require_once("config.php");

class MySQLDatabase {

private $connection;

function __construct(){
$this->open_connection();
}

public function open_connection() {
// $this->connection = mysql_connect();
$this->connection = mysqli_connect(DB_SERVER, DB_USER, DB_PASS);
if (!$this->connection)
{
// die("Database connection failed: " . mysql_error());
die("Database connection failed: " . mysqli_error());
}
else
{
// $db_select = mysql_select_db(DB_NAME, $this->connection);
$db_select = mysqli_select_db(DB_NAME, $this->connection);
if (!$db_select)
{
// die("Database selection failed: " . mysql_error());
die("Database selection failed: " . mysqli_error());
}
}
}

}


$database = new MySQLDatabase();


?>