Credits for Galleries

Hello,

I needed this feature, too and therefore implemented it:

// Finally check the galleries
        $pattern = get_shortcode_regex();
        if ( preg_match_all( '/'. $pattern .'/s', $post->post_content, $matches )
            && array_key_exists( 2, $matches )
            && in_array( 'gallery', $matches[2] ) )
        {
            foreach($matches[2] as $index => $tag){
                if($tag == 'gallery'){
                    $params = shortcode_parse_atts($matches[3][$index]);
                    if(isset($params['ids'])){
                        $ids = explode(',', $params['ids']);
                        foreach($ids as $id){
                            $id = (int) $id;
                            if($id > 0) $attachment_ids[] = $id;
                        }
                    }
                }
            }
        }

I also added functionality to make the IDs unique before the credits are requested from the DB:

// Make sure the ids only exist once
        $attachment_ids = array_unique($attachment_ids);