class DB extends mysqli {
public function __construct() {
parent::__construct($_SERVER['DB_HOST'],
$_SERVER['DB_USER'], $_SERVER['DB_PASS']);
}
}
这是一个非常浅薄的例子。
我上面讨论的多态性的一个例子是这样的:
class User implements DAO {
private $db;
public function __construct(DB $db) {
$this->db = $db;
}
}
//Testing code is simplified compared to using it in production
class TestDB extends DB {}
new User(new TestDB);
new User(new DB);