/**
  * @desc Deletes a contribution in the database.
  * @param Contribution $contribution The contribution to delete in the data base.
  */
 public static function delete_contribution($contribution)
 {
     //If it exists in database
     if ($contribution->get_id() > 0) {
         self::$db_querier->delete(DB_TABLE_EVENTS, 'WHERE id = :id', array('id' => $contribution->get_id()));
         //We reset the id
         $contribution->set_id(0);
         //Regeneration of the member cache file
         UnreadContributionsCache::invalidate();
     }
 }