Как я могу сделать, чтобы CodeIgniter загрузил определенные страницы с помощью SSL?

There are few ways to tackle this.

Option 1:

I would probably have the code deployed to both folders, then in the file: /system/application/config/config.php, set your page to:

$config['base_url'] = "http://www.yoursite.com/"; 

or

$config['base_url'] = "https://www.yoursite.com/";

Then in your non-ssl VirtualHost folder, set your config to redirect protected pages by folder to the SSL site:

RedirectPermanent /sslfolder https://www.yoursite.com/sslfolder

Option 2:

Send everything to SSL and keep all your code in one folder

/system/application/config/config.php, set your page to:

$config['base_url'] = "https://www.yoursite.com/";

Other Options

There are some more hacky ways to do this with header() redirects, etc. but I don't think you want to maintain different code bases for this option. I don't recommend this but you could do something like:

$config['base_url'] = “http://” . $_SERVER['http_host'] . “/”;