Imbo\Database\Mongo::getLastModified PHP Method

    public function getLastModified(array $users, $imageIdentifier = null)
    {
        try {
            // Query on the user
            $query = ['user' => ['$in' => $users]];
            if ($imageIdentifier) {
                // We want information about a single image. Add the identifier to the query
                $query['imageIdentifier'] = $imageIdentifier;
            }
            // Find a document
            $data = $this->getImageCollection()->findOne($query, ['sort' => ['updated' => -1], 'projection' => ['updated' => true]]);
        } catch (MongoException $e) {
            throw new DatabaseException('Unable to fetch image data', 500, $e);
        }
        if ($data === null && $imageIdentifier) {
            throw new DatabaseException('Image not found', 404);
        } else {
            if ($data === null) {
                $data = ['updated' => time()];
            }
        }
        return new DateTime('@' . $data['updated'], new DateTimeZone('UTC'));
    }