How do I add a link based on gallery owner id to the top nav?

I getting stuck with trying to write a simple module to add a link to the top menu which is based on the owner of the gallery album/item being viewed. I'm using the phpBB3 integration, and while this works perfectly and adds links to user profiles in phpBB to their own root album in Gallery2 it doesn't add anything links going back to the forum. It does put a mapping of gallery user id to phpBB user id into the ExternalIdMap table, so what I want to do is just add a single link to the top navigation that links to "memberlist.php?mode=viewprofile&u=<phpbbuserid>", where phpbbuserid is the value of externalId from the ExternalIdMap table for entityType "GalleryUser" where entityId is the userid of the album/item owner.

This is as far as I got, I just can't figure out what to do next:

class BBUserLinkModule extends GalleryModule {

    function BBUserLinkModule() {
	global $gallery;		
	$this->setId('bbuserlink');
	$this->setName('BB User Link');
	$this->setDescription($gallery->i18n('Add link for album/item to the owner profile in phpBB3.'));
	$this->setVersion('0.0.1');
	$this->setGroup('data', $gallery->i18n('Extra Data'));
	$this->setCallbacks('getSystemLinks');
	$this->setRequiredCoreApi(array(7, 10));
	$this->setRequiredModuleApi(array(3, 0));
    }

    /**
     * @see GalleryModule::getSystemLinks
     */

    function getSystemLinks()
    {

        global $item;

        $links = array();

        list ($ret, $g2_results) = GalleryCoreApi::getMapEntry('ExternalIdMap', array('externalId'), array('entityId' => $item->owner_id, 'entityType' => 'GalleryUser'));
        if ($ret) {return array($ret->wrap(__FILE__, __LINE__), null);  }

        foreach ($g2_results as $externalId )
        {
                $links['bbuserlink'] = array(
    	        'text' => $this->translate('Owner profile'),
                'params' => array('href' => '/memberlist.php?mode=viewprofile&u='.$externalId));
        }

	return array(null, $links);
    }


}

While it adds the link to the view album/item pages fine, the link has mapinfo in it rather than the externalId value which is I assume do the foreach part (I'm still learning PHP, associative arrays cause me a few problems as I'm used to array handling in VB6 and ASP which is very simplistic), and also I get errors in the site admin - which I assume is because $item isn't valid at that point but I can't figure out how to verify that $item is valid (I tried isset and testing it's value and this just caused other errors).

Can anyone help me with this?

Try http://gallery.menalto.com/apidoc/GalleryCore/Classes/GalleryEmbed.html#methodgetExternalIdMap

-s
FlashYourWeb and Your Gallery with The E2 XML Media Player for Gallery2

list ($ret, $user) = GalleryEmbed::getExternalIdMap('entityId');
$link = '/memberlist.php?mode=viewprofile&u='.$user[$item->owner_id][externalId];

-s
FlashYourWeb and Your Gallery with The E2 XML Media Player for Gallery2

Thanks for that, but doesn't that end up returning an array of all the user mappings? I've got over 800 users at the moment and surely it's more efficient to query for just the single id that is required isn't it?

But $user is an array containing all the externalmapid table data, isn't it? That will have, at present, over 800 array elements, each with 3 values (entityId, externalId, and entityType). Assuming 8 bit ints for the Ids, that's 27 bits of data per map entry plus array overheads, which is at least 21kB of data (and will increase as I get more users signing up) to be read into and released from memory at every hit to a page. Requesting just the single entityId should be significantly less than this. While 21kb isn't much right now I think I'll stick to the code I've figured out myself. Thanks for the suggestion though, if I hadn't managed to work out how to use the results from getMapEntry it would have been a useful temporary solution.