Piwik\Common::convertVisitorIdToBin PHP Method

    public static function convertVisitorIdToBin($id)
    {
        if (strlen($id) !== Tracker::LENGTH_HEX_ID_STRING || @bin2hex(self::hex2bin($id)) != $id) {
            throw new Exception("visitorId is expected to be a " . Tracker::LENGTH_HEX_ID_STRING . " hex char string");
        }
        return self::hex2bin($id);
    }

 public function sendMessage($content, $fromAdmin = false, $idAutoMsg = false)
 {
     $hexVisitorId = Common::convertVisitorIdToBin($this->idvisitor);
     $sanitizeContent = Common::sanitizeInputValues($content);
     $additionnalParams = "";
     $microtime = microtime(true);
     $arguments = array($this->idsite, $hexVisitorId, $sanitizeContent, $microtime);
     if ($idAutoMsg) {
         $additionnalParams .= ", idautomsg = ?";
         $arguments[] = $idAutoMsg;
     }
     if ($fromAdmin) {
         $additionnalParams .= ", answerfrom = ?";
         $arguments[] = $fromAdmin;
     }
     $queryResult = Db::query("INSERT INTO " . Common::prefixTable('chat') . " SET idsite = ?, idvisitor = ?, content = ?, microtime = ?{$additionnalParams}", $arguments);
     if (!$fromAdmin) {
         ChatAcknowledgment::setLastSent($this->idsite, $this->idvisitor, $microtime);
         //ChatMail::sendNotificationToAdmin($this->idsite, $this->idvisitor, $sanitizeContent);
     }
     $insertedRow = Db::fetchRow("SELECT idmessage,microtime FROM " . Common::prefixTable('chat') . " WHERE idvisitor = ? AND microtime = ?", array($hexVisitorId, $microtime));
     return $insertedRow;
 }