[PHP][OOP] Błąd z prepare Opcje

[Dominator]

[PHP] pobierz, plaintext 
Class User
{
	public function getUsername($id)
	{
		try
		{
			$pdo = new DB("","","","","");
			$sqlprep = $pdo->prepare("XX");
			$sqlprep->execute();
		}
		catch(PDOException $e)
		{
			echo "Error! Code ->".$e->getMessage();
		}
	}
}
 
$usr = new User();
$usr -> getUsername("65");
[PHP] pobierz, plaintext 

Taki jest błąd: Fatal error: Call to undefined method DB::prepare() in
Co zrobiłem źle?

---
Tak wygląda klasa do łączenia się z bazą:

[PHP] pobierz, plaintext 
Class DB
{
	protected $server;
	protected $port ;
	protected $user;
	protected $password;
	protected $database;
	protected $db;
	public function __construct($server, $port, $username, $password, $database)
	{
		$this->Set($server, $port, $username, $password, $database);
		$this->Connect();
	}
	protected function Set($server, $port, $username, $password, $database)
	{
		$this->server = $server;
		$this->port = $port;
		$this->user = $username;
		$this->password = $password;
		$this->database = $database;
	}
	protected function Connect()
	{
		$pdo = new PDO('mysql:host='.$this->server.';dbname='.$this->database.';port='.$this->port, $this->user, $this->password );
		$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
	}
}
[PHP] pobierz, plaintext