为什么php的mail()函数发送邮件成功但字段为空？

电子邮件已到达目标地址，但字段为空。原因是什么？

我的使用mail()如下：

<?php
header('Content-type: application/json');
$status = array(
'type'=>'success',
'message'=>'Email sent!'
);

$name = @trim(stripslashes($_POST['name'])); 
$email = @trim(stripslashes($_POST['email'])); 
$subject = @trim(stripslashes($_POST['subject'])); 
$message = @trim(stripslashes($_POST['message'])); 

$email_from = $email;
$email_to = '[email protected] /cdn-cgi/l/email-protection';

$body = 'Name: ' . $name . "\n\n" . 'Email: ' . $email . "\n\n" . 'Subject: ' . $subject . "\n\n" . 'Message: ' . $message;

$success = @mail($email_to, $subject, $body, 'From: <'.$email_from.'>');

echo json_encode($status);
die; 
?>

HTML 格式为：

<form id="main-contact-form" class="contact-form" name="contact-form" method="post" action="sendemail.php" role="form">
<div class="row">
<div class="col-sm-6">
<div class="form-group">
<input type="text" class="form-control" required placeholder="Name" name="name" id="name">
</div>
</div>
<div class="col-sm-6">
<div class="form-group">
<input type="text" class="form-control" required placeholder="Email address" name="email" id="email">
</div>
</div>
</div>
<div class="row">
<div class="col-sm-12">
<div class="form-group">
<textarea name="message" id="message" required class="form-control" rows="8" placeholder="Message" name="message" id="message"></textarea>
</div>
<div class="form-group">
<button type="submit" class="btn btn-danger btn-lg">Send Message</button>
</div>
</div>
</div>
</form>

$subject = @trim(stripslashes($_POST['subject']));但您的表单没有主题，您应该添加它。
不要用@抑制错误，因为你永远不会知道你的代码到底发生了什么。