public function createStream($channel, $firstUpdate)
 {
     $db = new Database();
     /** @var TwitterEntity $result */
     $result = $this->getStreamByChannel($channel);
     if ($result) {
         //Si existe deja, et nouvelle date plus ancienne, alors on modifie le firstUpdate a la nouvelle date donnee
         if (strtotime($firstUpdate) < strtotime($result->getFirstUpdate())) {
             $db->execute('UPDATE stream_twitter SET firstUpdate = ? WHERE channel = ?', array(date(Database::DATE_FORMAT, strtotime($firstUpdate)), $channel));
         }
         return $result;
     } else {
         //Sinon, on cree le flux
         $twitterEntity = new TwitterEntity();
         $twitterEntity->setChannel($channel);
         $twitterEntity->setFirstUpdate($firstUpdate);
         $twitterEntity->setLastUpdate(date(Database::DATE_FORMAT));
         $twitterEntity->persist();
         return $twitterEntity;
     }
 }