framework/caching/FileCache.php
protected function getCacheFile($key)
    {
        if ($this->directoryLevel > 0) {
            $base = $this->cachePath;
            for ($i = 0; $i < $this->directoryLevel; ++$i) {
                if (($prefix = substr($key, $i + $i, 2)) !== false) {
                    $base .= DIRECTORY_SEPARATOR . $prefix;
                }
            }

            return $base . DIRECTORY_SEPARATOR . $key . $this->cacheFileSuffix;
        }

        return $this->cachePath . DIRECTORY_SEPARATOR . $key . $this->cacheFileSuffix;
    }
protected function getCacheFile($key)
    {
        if ($this->directoryLevel > 0) {
            $base = $this->cachePath;
            for ($i = 0; $i < $this->directoryLevel; ++$i) {
                if (($prefix = substr($key, $i + $i, 2)) !== false) {
                    $base .= DIRECTORY_SEPARATOR . $prefix;
                }
            }

            return $base . DIRECTORY_SEPARATOR . $key . $this->cacheFileSuffix;
        }

        return $this->cachePath . DIRECTORY_SEPARATOR . $key . $this->cacheFileSuffix;
    }
Returns the cache file path given the cache key.
@param string $key cache key
@return string the cache file path