Cake\Chronos\ChronosInterval::__toString PHP Method

    public function __toString()
    {
        $date = array_filter([static::PERIOD_YEARS => $this->y, static::PERIOD_MONTHS => $this->m, static::PERIOD_DAYS => $this->d]);
        $time = array_filter([static::PERIOD_HOURS => $this->h, static::PERIOD_MINUTES => $this->i, static::PERIOD_SECONDS => $this->s]);
        $specString = static::PERIOD_PREFIX;
        foreach ($date as $key => $value) {
            $specString .= $value . $key;
        }
        if (count($time) > 0) {
            $specString .= static::PERIOD_TIME_PREFIX;
            foreach ($time as $key => $value) {
                $specString .= $value . $key;
            }
        }
        return $specString === static::PERIOD_PREFIX ? 'PT0S' : $specString;
    }