src/Service/Driver/File.php
public function get($key)
    {
        $file = $this->getFilename($key);
        if (file_exists($file)) {
            return (new \DateTime())->setTimestamp(filemtime($file));
        }

        return;
    }
public function get($key)
    {
        $file = $this->getFilename($key);
        if (file_exists($file)) {
            return (new \DateTime())->setTimestamp(filemtime($file));
        }

        return;
    }
@param string $key

@return \DateTime|null