Require a complex password.

[leebaird]

    if(strlen($_POST['password']) < 12) {
        die("Your password is too short. The minimum length is 12 characters.");
    }

    if(!preg_match("#[A-Z]+#", ($_POST['password']))) {
        die("Your password must contain at least one uppercase letter.");
    }

    if(!preg_match("#[a-z]+#", ($_POST['password']))) {
        die("Your password must contain at least one lowercase letter.");
    }

    if(!preg_match("#[0-9]+#", ($_POST['password']))) {
        die("Your password must contain at least one number.");
    }

    if(!preg_match("#[\W]+#", ($_POST['password']))) {
        die("Your password must contain at least one special character.");
    }

[Nilpo]

If someone wants to increase password complexity, this is a good example of how to do it. However, there is quite of strong argument against using complex passwords in favor of using complex passphrases. For that reason, and since this is a very basic login system, I would not include it in this project. Perhaps another branch should be created with more production ready code.