[kh99]

You want to do something like:

$query = $db->query_read("SELECT value, varname FROM ".TABLE_PREFIX."setting WHERE varname IN ('illegalusernames','minuserlength ','maxuserlength')");

while ($results = $db->fetch_array($query))
{
    print_r($results);
}

Edit: Oops, just noticed that Lynne beat me to that first reply. Anyway, you also have an extra space in the 'minuserlength' string.