[Database Access] Class w/ PDO #PHP

Database.php

class Database
{
    private static $datasource = 'mysql:host=localhost; dbname=mydbname';
    private static $username = 'root';
    private static $password = 'root';
    private static $pdo;

    public static function getPDO()
    {
        if (!isset(self::$db)) {
            self::$pdo = new PDO(self::$datasource, self::$username, self::$password);
        }
        return self::$pdo;
    }
}