class DurationIso8601

class DurationIso8601 extends StringData implements DurationInterface {
    
    /**
     * {@inheritdoc}
     */
    public function getDuration() {
        if ($this->value) {
            // @todo Add support for negative intervals on top of the DateInterval
            // constructor.
            return new \DateInterval($this->value);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function setDuration(\DateInterval $duration, $notify = TRUE) {
        // Generate an ISO 8601 formatted string as supported by
        // DateInterval::__construct() and setValue().
        $this->value = $duration->format('%rP%yY%mM%dDT%hH%mM%sS');
        // Notify the parent of any changes.
        if ($notify && isset($this->parent)) {
            $this->parent
                ->onChange($this->name);
        }
    }

}