[eluser]Iván Argulo[/eluser]
Well, I think we're missing something...
If you redirect to welcome2.php, you would get a 404 error, because you need a controller called welcome2.php, and, AFAIK, it's not possible.
So, you'll need the following structure:
application/controlers/welcome2.php
application/views/welcome2.php
And then, you'll have to redirect to site_url('welcome2') **NOTE** without extension .php.
Are you used to the MVC approach? Please, put here your controllers and views, so we can see them and find the error.