Piwik API setVisitorId not stores into DB (no replies)

Hi,

I have integrated piwik with use of php API and it works OK except one think which is custom id not stores into database, piwik generates its own "setVisitorId" code. my code is:

$t = new PiwikTracker( 2, 'http://site.com/piwik');
$t->setTokenAuth( 'codes' );
$t->setIp( $_SERVER['REMOTE_ADDR'] );
$t->doTrackPageView($page_id);
$t->setUrl( "http://".$_SERVER[HTTP_HOST].$_SERVER[REQUEST_URI] );

                     $t->setVisitorId( "66200c7d6e4ec962" );
$t->setUserAgent( @$_SERVER['HTTP_USER_AGENT']);
$t->setBrowserLanguage(@$_SERVER['HTTP_ACCEPT_LANGUAGE']);

please let me know what could be the reason for this.

Thanks in advance.