Calculate MD5 of file being downloaded with PHP and CURL

I have some cURL call that download a large file. I'm wondering if it is possible to calculate hash when the file is still downloading?

I think the progress callback function is the right place for accomplish that..

function get($urlget, $filename) {

        //Init Stuff[...]                   

        $this->fp = fopen($filename, "w+");
        $ch = curl_init();       


        //[...] irrelevant curlopt stuff

        curl_setopt($ch, CURLOPT_FILE, $this->fp);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($ch, CURLOPT_NOPROGRESS, 0);
        curl_setopt($ch, CURLOPT_PROGRESSFUNCTION, array($this,'curl_progress_cb'));

        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

        $ret = curl_exec($ch);

        if( curl_errno($ch) ){
            $ret = FALSE;
        }

        curl_close($ch);

        fclose($this->fp);        

        return $ret;
    }

    function curl_progress_cb($dltotal, $dlnow, $ultotal, $ulnow ){
        //... Calculate MD5 of file here with $this->fp

    }

Its possible to calculate md5 hash of partially downloaded file, but it does not make too much sense. Every downloaded byte will change your hash diametrally, what is the reason behind going with this kind solution?

If you need to have md5 hash for entire file than the answer is NO. Your program has to first download the file and then generate the hash.