FluidTYPO3\Vhs\ViewHelpers\Format\Json\EncodeViewHelper::recursiveDateTimeToUnixtimeMiliseconds PHP Method

    protected function recursiveDateTimeToUnixtimeMiliseconds(array $array, $dateTimeFormat)
    {
        foreach ($array as $key => $possibleDateTime) {
            if (true === $possibleDateTime instanceof \DateTime) {
                $array[$key] = $this->dateTimeToUnixtimeMiliseconds($possibleDateTime, $dateTimeFormat);
            } elseif (true === is_array($possibleDateTime)) {
                $array[$key] = $this->recursiveDateTimeToUnixtimeMiliseconds($array[$key], $dateTimeFormat);
            }
        }
        return $array;
    }