public function query ($sql, array $bound_parameters = array(), $fetch = true) {

		$statement = $this -> entity_manager -> getConnection() -> prepare($sql);

		foreach ($bound_parameters as $parameter => $value) {
			$statement -> bindValue($parameter, $value);
		}

		$statement -> execute();

		if ($fetch) {
			return $statement -> fetchAll();
		} else {
			return null;
		}
	}