PHP：在准备好的语句上获得插入确认

`unblocker_users` (
  `uno` bigint(20) NOT NULL AUTO_INCREMENT,
  `user_email` varchar(210) DEFAULT NULL,
  `pw_hash` varchar(30) DEFAULT NULL,
  `email_confirmed` tinyint(4) DEFAULT NULL,
  `total_requests` bigint(20) DEFAULT NULL,
  `today_date` date DEFAULT NULL,
  `accessed_today` tinyint(4) DEFAULT NULL,)

function add_new_user($e_mail1)
    {
    require_once \"db.php\";

$stmt = $mysqli->prepare(\"INSERT INTO unblocker_users VALUES (\'\',?, ?,0,0,?,0)\");
$stmt->bind_param(\'sss\', $e_mail1, $this->genRandomString(1),$this->today_date()); 

$stmt->execute();

$stmt->close(); 
// ####### Below line is giving an error ########
$done = $stmt->affected_rows;

return $done;
    }

Warning: unblocker_class::add_new_user() [unblocker-class.add-new-user]: Property access is not allowed yet in...