返回错误消息未显示 - if else条件

Question

很抱歉在这里问愚蠢的问题。问题是我没有收到错误消息。我的意思是，如果电子邮件或密码不正确，我想打印这一行：

'{"status":"false","message":"Login incorrect. Try again"}';

我已尝试过此代码。

else if($email != $dbemail || $password != $dbpassword) { return '{"status":"false","message":"Login incorrect. Try again"}'; }

但没有得到别的消息。

if ($checkDevice != 0 ) {

                     $email = $get['email'];
                     $password = $get['password'];

                            $stmt = $con->prepare("SELECT * FROM users WHERE email = ? AND password = ? ");
                            $con->errorInfo();
                            $stmt->bindParam('1', $email, PDO::PARAM_STR);
                            $stmt->bindParam('2', $password, PDO::PARAM_STR);
                            $stmt->execute();
                            $num_rows = $stmt->rowCount();
                            // print_r($get);

                            if($num_rows != 0 )
                            {
                                while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) 
                                {
                                    $dbemail = $row['email'];
                                    $dbpassword = $row['password'];
                                }
                                  if($email == $dbemail && $password == $dbpassword) 
                                  {
                                    return '{"status":"true","message":"Success. Login details correct."}';
                                  }
                                  else
                                  {   
                                    return '{"status":"false","message":"Login incorrect. Try again"}';
                                  }
                            }
                }