错误消息不会显示在相应的输入字段下。使用 HTML、PHP-PHP中文网问答

如果用户输入无效数据，如何立即在输入字段下显示相应的错误消息。例如，用户在“名称”字段中输入无效数据，错误消息立即出现在名称字段下。 “电子邮件”和“消息”字段也是如此。我正在使用下一个 HTML 和 PHP 代码：

SMTPDebug = SMTP::DEBUG_SERVER;

        $mail->isSMTP();
        $mail->SMTPAuth = true;

        $mail->Host = "smtp.gmail.com";
        $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
        $mail->Port = 587;

        require_once 'config.php';
        $mail->Username = SMTP_USERNAME;
        $mail->Password = SMTP_PASSWORD;

        $mail->setFrom($emailSanitized, $nameSanitized);
        $mail->addAddress("myemail@gmail.com", "myemail");

        $mail->Subject = $subject;
        $mail->Body =  "Name: $nameSanitized\nEmail: $emailSanitized\n\n$messageSanitized";
        $mail->send();

        header("Location: sent.html");
    } catch (Exception $e) {
        echo 'Message could not be sent. Mailer Error: ', $mail->ErrorInfo;
    }
} else {
 
    echo $emailErr;
    echo $nameErr;
    echo $messErr;

}
?>

我尝试了不同的文章。

} else { ?> <form method="POST" action="send-email.php"> <input type="text" name="name" id="name" placeholder="Name*" required> <div class="error"><?php echo $nameErr ?></div> <input type="email" name="email" id="email" placeholder="Email*" required> <div class="error"><?php echo $emailErr ?></div> <textarea name="message" id="message" placeholder="Your Message*" required></textarea> <div class="error"><?php echo $messErr ?></div> <button type="submit" name="submit" id="submit" class="button">Start</button> </form> <?php }