public function collectFiles(FileEvent $e)
    {
        $this->appendPDF = array();
        $files = $e->getAllFiles();
        foreach ($files as $name => $file) {
            if (!empty($file) && $file instanceof FileEntity) {
                if (0 === strpos($file->getType(), 'image')) {
                    $this->appendImage[] = $file;
                }
                if (strtolower($file->getType()) == 'application/pdf') {
                    $this->appendPDF[] = $file;
                }
            }
        }
        return null;
    }