Inserting into table twice..:(

[eluser]WanWizard[/eluser]
So, what happens if you type "http://yourwebsite/members/memberadd" in your browser?
It would just call your models add_member() method without a valid $id and with an empty $_POST array.

So again, check for multiple calls, possibly due to rewrite issues. The first request will be the post of the form, the second one an HTTP GET which will do the same as typing the URL in the browser.

Your logic is flawed. If you're going to process form data, make sure there's a form posted, and display an error message and/or redirect to the form if not.