public static function search($s, $per_page = null)
 {
     global $wpdb;
     $model = new MM_Conversation_Model();
     if (!empty($s)) {
         if (!$per_page) {
             $per_page = mmg()->setting()->per_page;
         }
         $paged = mmg()->get('mpaged', 1);
         $offset = ($paged - 1) * $per_page;
         $total_pages = ceil(self::count_all() / $per_page);
         mmg()->global['conversation_total_pages'] = $total_pages;
         if (is_admin()) {
             $sql = "SELECT conversation.id FROM wp_mm_conversation conversation\r\n                    INNER JOIN wp_mm_status mstat ON mstat.conversation_id = conversation.id\r\n                    INNER JOIN wp_postmeta meta ON meta.meta_key='_conversation_id' AND meta.meta_value = conversation.id\r\n                    INNER JOIN wp_posts posts ON posts.ID = meta.post_id\r\n                    INNER JOIN wp_users users ON users.id = posts.post_author\r\n                    WHERE (posts.post_title LIKE %s OR posts.post_content LIKE %s OR users.user_login LIKE %s) AND site_id=%d\r\n                    GROUP BY conversation.id LIMIT %d,%d";
             $sql = $wpdb->prepare($sql, "%{$s}%", "%{$s}%", "%{$s}%", get_current_blog_id(), $offset, $per_page);
         } else {
             $sql = "SELECT conversation.id FROM wp_mm_conversation conversation\r\n                    INNER JOIN wp_mm_status mstat ON mstat.conversation_id = conversation.id\r\n                    INNER JOIN wp_postmeta meta ON meta.meta_key='_conversation_id' AND meta.meta_value = conversation.id\r\n                    INNER JOIN wp_posts posts ON posts.ID = meta.post_id\r\n                    INNER JOIN wp_users users ON users.id = posts.post_author\r\n                    WHERE mstat.user_id= %d AND (posts.post_title LIKE %s OR posts.post_content LIKE %s OR users.user_login LIKE %s) AND site_id=%d\r\n                    GROUP BY conversation.id LIMIT %d,%d";
             $sql = $wpdb->prepare($sql, get_current_user_id(), "%{$s}%", "%{$s}%", "%{$s}%", get_current_blog_id(), $offset, $per_page);
         }
         $ids = $wpdb->get_col($sql);
         $ids = array_filter(array_unique($ids));
         if (empty($ids)) {
             return array();
         }
         $models = $model->find_all_by_ids($ids, false, false, 'date_created DESC');
         return $models;
     } else {
         return self::get_conversation();
     }
 }