Well, there are 2 things specially i dont like in that thing
PHP Code:
mysql_query("insert into pw_whois (eventid, username, userid) values ('7', '$bbuserinfo[username]', '$bbuserinfo[userid]')");
//Send the user back to the calendar
echo ("<html><body onload=document.location.href='http://www.powwows.com/gathering/pw_calendar/pw_event_display.php?eventid=7'></body></html>");
You can make thse 2 nicer if you FIRST use the database class of the board and SECOND if you redirect by header (wich is smother).
Would look like this for your example:
PHP Code:
$DB_site->query("insert into pw_whois (eventid, username, userid) values ('7', '$bbuserinfo[username]', '$bbuserinfo[userid]')");
//Send the user back to the calendar
header ("Location: [url]http://www.powwows.com/gathering/pw_calendar/pw_event_display.php?eventid=7[/url]");
But i would not do a full url in these scripts, make it more variable, this saves you headaches. Feel free to copy paste this.
The reason to use the class is, that you use the data from the class AND use the same error reporting tools. If something happens, you get informed...