private function getPhoto($url)
 {
     $photo = $this->photo_model->getByField('url', $url);
     if (!$photo) {
         $this->private_hash = photosPhotoModel::parsePrivateUrl($url);
         $photo = $this->photo_model->getByField('hash', $this->private_hash);
         $parent = $this->photo_model->getStackParent($photo);
         $this->hash = photosPhotoModel::getPrivateHash($parent ? $parent : $photo);
     }
     return $photo;
 }