private function formatDuration($duration)
{
preg_match_all("/PT(\\d+H)?(\\d+M)?(\\d+S)?/", $duration, $matches);
$hours = strlen($matches[1][0]) == 0 ? 0 : substr($matches[1][0], 0, strlen($matches[1][0]) - 1);
$minutes = strlen($matches[2][0]) == 0 ? 0 : substr($matches[2][0], 0, strlen($matches[2][0]) - 1);
$seconds = strlen($matches[3][0]) == 0 ? 0 : substr($matches[3][0], 0, strlen($matches[3][0]) - 1);
return 3600 * $hours + 60 * $minutes + $seconds;
}