[Lynne]

The existing php code is in the vbulletin files. Did you try a search in the files for fetch_userinfo? It shows up many times and you can see the use of it. These are some excepts from a page I use:

First the cleaner is used on the userid that is passed from the form:

PHP Code:

$vbulletin->input->clean_array_gpc('r', array(
    'f'    => TYPE_UINT,
    'do'  => TYPE_STR,
    'u'    => TYPE_UINT,
)); 


then the userinfo is obtained a few lines after and I grab the username (and other stuff later):

PHP Code:

      $userinfo = fetch_userinfo($vbulletin->GPC['u']);
        $username = $userinfo['username']; 


Take a look at the function itself to see all the info obtained in the query - in includes/functions.php

There are articles you can read on the user of the vbulletin cleaner and on writing secure code.