class YourParser{

    var $curl; // cURL handle
    var $cache_dir = 'cache_dir';

    function YourParser() {
        // Constructor

        // Set up libcurl
        $this->curl = curl_init();
        curl_setopt($this->curl, CURLOPT_FAILONERROR, 1);
        curl_setopt($this->curl, CURLOPT_RETURNTRANSFER,1); // return into a variable
        curl_setopt($this->curl, CURLOPT_FOLLOWLOCATION, 1); // allow redirects
    }

    function fetch($url, $cache_life = 0) {
        // Fetches a page with libcurl. Cache life measured in seconds. Returns the page content as a string.
        // Does not yet support POST form fields.

        if ($cache_life <= 0) {
            // Caching is disabled.
            // Download the page
            curl_setopt($this->curl, CURLOPT_URL, $url);
            return (curl_exec($this->curl));
        } else {
            // Caching is enabled.
            $cached_fn = $this->cache_dir.'/'.md5($url);
            $cached = file_get_contents($cached_fn);
            if ($cached === false) {
                // Could not open cached version of the file.
                curl_setopt($this->curl, CURLOPT_URL, $url);
                $results = curl_exec($this->curl);
                // Write it to cache and return it
                if (file_put_contents($cached_fn, $results) === false) {
                    // Failed writing to cache. Not writable?
                }
                return ($results);
            } else {
                // Cached file retrieved successfully
                // test age
                $age = time() - filemtime($cached_fn);
                if ($age < $cache_life) {
                    // Cache is still alive
                    return ($cached);
                } else {
                    // Cache is expired
                    curl_setopt($this->curl, CURLOPT_URL, $url);
                    $results = curl_exec($this->curl);
                    // Write it to cache and return it
                    if (file_put_contents($cached_fn, $results) === false) {
                        // Failed writing to cache. Not writable?
                    }
                    return ($results);
                }
            }
        }
    }
}