public static function getArchiveSingleton()
 {
     if (null === self::$instance) {
         self::$instance = new FooArchive();
     }
     return self::$instance;
 }
 public function findOne()
 {
     $archive = FooArchiveCollection::getArchiveSingleton();
     $archive->setId($this->pk);
     return $archive;
 }