public function getTempDirectory()
    {
        if (is_null($this->tempDirectory)) {
            $root = sys_get_temp_dir();
            if (!is_dir($root . '/humbug')) {
                mkdir($root . '/humbug', 0777, true);
            }
            $this->tempDirectory = $root . '/humbug';
        }
        return $this->tempDirectory;
    }