Actually i Want to people to be able to use a certain displayname. But not to take a Displayname that has already been taken. (to make my users to be able to use swedishletters and odd symbols in their name.
Mostly managed to write something, need to work on the error page though.
<?php
/*
Plugin Name: No Duplicate Display Names
Description: Prevents users from using already existing display names.
*/
function check_display_name ( $user_id ) {
global $bbdb, $bb_current_id, $display_name;
$name_query = <<<EOQ
SELECT
user_login
FROM
$bbdb->users
WHERE
display_name = "$display_name"
AND
ID != "$bb_current_id"
EOQ;
if ( $name_clash = $bbdb->get_var( $name_query ) ) {
wp_redirect( add_query_arg( 'nameclash', $name_clash, get_user_profile_link( $user->ID ) ) );
exit;
}
}
add_action ( 'before_profile_edited', 'check_display_name' );
?>
You also need in your theme’s profile.php, before the line <?php elseif ( $user_id == bb_get_current_user_info( ‘id’ ) ) : ?>
<?php elseif ( $_GET['nameclash'] ) : ?>
<div class="notice error">
<p><?php printf(__('Display name already taken by %s'), $_GET['nameclash' ]); ?>. <a href="<?php profile_tab_link( $user_id, 'edit' ); ?>"><?php _e('Edit again »'); ?></a></p>
</div>
Also, I just set my display name to a SQL query string, yay 
Hmmm Got this error message:
Warning: Unexpected character in input: ” (ASCII=92) state=1 in /home/bajentes/public_html/bbpress/my-plugins/no-duplicate-displayname/no-duplicate-displayname.php on line 2
Parse error: syntax error, unexpected T_STRING in /home/bajentes/public_html/bbpress/my-plugins/no-duplicate-displayname/no-duplicate-displayname.php on line 2
What to do….
Ah – problem fixed. Text was screwed up.
next problem:
Warning: Cannot modify header information – headers already sent by (output started at /home/bajentes/public_html/bbpress/my-plugins/no-duplicate-displayname/no-duplicate-displayname.php:32) in /home/bajentes/public_html/bbpress/bb-includes/functions.bb-pluggable.php on line 232
Check for an extra line or space after the closing ?> tag, seems to be a common problem copying from the forums. Or an extra line or space before the <?php tag.
kawuso,
Is it possible to make the plugin to “forbid” or dont register a change to a displayname that has already been taken.
As it is now, you get a errormessage. But if you ignore the message telling you to edit. you can still post replys in a already taken displayname…
That’s… weird, and slightly worrying. Unless you mean can it stop people already registered with a duplicate name already? It could, but that’d be easily avoidable by never editing your profile. If it’s registering changes to an already existing display name from a different one though, there’s something very wrong, because it’s run before anything is saved and has a hard stop put in right after the redirect.
kawuso,
like this,
If this was my forum I´d go to edit my profile and try to use change my name to show to yours. What happens is that i get the error message that tells me to edit my displayname again.
If I instead ignore the message and go back to the forum – I´ll have your name as name with my avatar.
How fun, your install is ignoring a exit (die) command got a link to your forum?
That or 1.0.2 is radically different in how it structures when that function is called 
I couldn’t reproduce getting the error, only changing and getting the okay message. No idea why that is, but my money is because of MySQL and UTF-8. Maybe someone else can fix that, but I definitely can’t for now.
Kawauso, you buddypress knowledgeable, I want to use this on my site but I don’t use bbpress registration.
kawuso,
thanks for your help. I´ll let it stay the way it is. If our user ignores the errormessage I´ll suppose they have to be handled in other ways.
Thanks again
@gerikg: There’s far more chance that someone has written something like this for WordPress in their plugin database
Thanks Kawauso, haven’t had luck finding it though.
