Pico::discoverRequestFile PHP Method

    protected function discoverRequestFile()
    {
        if (empty($this->requestUrl)) {
            $this->requestFile = $this->getConfig('content_dir') . 'index' . $this->getConfig('content_ext');
        } else {
            // prevent content_dir breakouts using malicious request URLs
            // we don't use realpath() here because we neither want to check for file existance
            // nor prohibit symlinks which intentionally point to somewhere outside the content_dir
            // it is STRONGLY RECOMMENDED to use open_basedir - always, not just with Pico!
            $requestUrl = str_replace('\\', '/', $this->requestUrl);
            $requestUrlParts = explode('/', $requestUrl);
            $requestFileParts = array();
            foreach ($requestUrlParts as $requestUrlPart) {
                if ($requestUrlPart === '' || $requestUrlPart === '.') {
                    continue;
                } elseif ($requestUrlPart === '..') {
                    array_pop($requestFileParts);
                    continue;
                }
                $requestFileParts[] = $requestUrlPart;
            }
            if (empty($requestFileParts)) {
                $this->requestFile = $this->getConfig('content_dir') . 'index' . $this->getConfig('content_ext');
                return;
            }
            // discover the content file to serve
            // Note: $requestFileParts neither contains a trailing nor a leading slash
            $this->requestFile = $this->getConfig('content_dir') . implode('/', $requestFileParts);
            if (is_dir($this->requestFile)) {
                // if no index file is found, try a accordingly named file in the previous dir
                // if this file doesn't exist either, show the 404 page, but assume the index
                // file as being requested (maintains backward compatibility to Pico < 1.0)
                $indexFile = $this->requestFile . '/index' . $this->getConfig('content_ext');
                if (file_exists($indexFile) || !file_exists($this->requestFile . $this->getConfig('content_ext'))) {
                    $this->requestFile = $indexFile;
                    return;
                }
            }
            $this->requestFile .= $this->getConfig('content_ext');
        }
    }