Referrer problem

i use my own js stat code on client side, on the server side i use piwik api to send stat results to piwik. the problem is that i cant write referrer. I can see it in api and i do send it to piwik but in db referer_url is empty. what have i done wrong?

$PiwicTracer = new PiwikTracker( $site_data_res[‘piwik_site_id’], $this->pw_domain );
$PiwicTracer->setUserAgent( $this->c_browser);
$PiwicTracer->setIp( $this->ip );
$PiwicTracer->setForceVisitDateTime( $this->server_time );
$PiwicTracer->setUrl( $this->current_page );
$PiwicTracer->setUrlReferrer($this->referer);// i thought this should write referrer

$this->referer was without “http://”