Manual talk:Hooks/AbortNewAccount

Question: Where should I insert this code?

Create an extension with a php function that is then hooked to the hook. Add extension to Localsettings.php.

Question: What information is available in the $user Variable?

You can basically access all information, which the user has provided. --88.130.67.9 18:20, 25 April 2013 (UTC)

Question: How can I access the E-Mail address entered by the user in the login/create account email field?

Check the functions in User.php; those are the ones you can use to get the information. So for the email address it would be $providedEmailAddress = $user->getEmail();. --88.130.67.9 18:20, 25 April 2013 (UTC)