public function save_activity($activity_id = 0, $date = 0, $amount = 0, $tariffs_id = 0, $travel_distance = 0, $travel_description = '', $expenses = 0, $ticket_number = '', $comment = '')
{
// First check if timesheet has been saved previously (id != 0)
// If not, first save current timesheet
if ($this->id == 0) {
$this->save();
}
// Save activity
$activity = new activity($activity_id);
$activity->fill($date, $amount, $tariffs_id, $travel_distance, $travel_description, $expenses, $ticket_number, $comment, $this->id);
$activity->save();
}
