How can I add extra fields in the user profiles (without using smartprofiles)?

Second question: if I use smartprofiles - how can I combine smartprofiles fields with the core user registration form?

1. one of the easiest method is you can change the language definition of unused fields such as icq, aim etc
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see an example
here on how to make this extra field appear in registration page...


** on XOOPS future release (3.0) from what i understand the profile module will be improved and addition of new fields will be easy

2. if i'm not mistaken smartprofile has it own register form page that the user will use to register themselves and you can customize it...you'll need to use htaccess file to redirect the default register.php to smartprofile/register.php

Smartprofile integrates the core fields if youset it up in the admin side.

Without using modules to extend user profile you will have to Hack XOOPS core.
For adding more fields hacking the core you must:
Add a field in the "users" table.
Edit kernel/user.php so the extra field becomes available in $xoopsUser object (ex: $xoopsUser->getVar('myextrafield') )
Then you must edit forms and templates to get/show information.

It is not that hard but anyway, is better to keep away from hacking, it will get you extra work if you need to update the core.