protected function getPath($key)
    {
        if ($this->humanReadable) {
            $path = $this->sanitizeReadableFileName($key);
        } else {
            $encoded = hash('md5', $key);
            $path = implode(DIRECTORY_SEPARATOR,str_split(substr($encoded, 0, $this->levels))).DIRECTORY_SEPARATOR.$encoded;
        }
        return  $this->directory.$path.'.php';
    }