我有一个简单的联系表格无法发送，我是PHP的新手，所以很可能我忘记了什么或代码错误。我知道这里有很多关于同一主题的问题，但我不确定我的代码。
我收到错误消息：未定义的索引：在第 31 行发送 ''mail.php
.HTML
<html>
<head>
<title>form</title>
</head>
<body>
<h2>Contact Form</h2>
<form id="form_id" name="form_name" action="mail.php" method="post">
<div>
<input type="text" name="name" id="name" placeholder="Name" required/>
</div>
<div>
<input type="email" name="email" id="email" placeholder="Email" required/>
</div>
<div>
<input type="number" name="tel" id="tel" placeholder="Phone" required/>
</div>
<textarea name="message" type="text" id="message" rows="5" cols="30" placeholder="Message" required></textarea>
</div>
<div>
<input type="submit" name="submit" value="submit" />
</div>
</form>
</body>
</html>
.PHP
<?php
$to = 'test@gmail.com';
$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];
$tel = $_POST['tel'];
$body = <<<EMAIL
This is a message for your website.
Name: $name
Email: $email
Tel: $tel
Message: $message
EMAIL;
// To send HTML mail, the Content-type header must be set
$headers = 'MIME-Version: 1.0' . "'r'n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "'r'n";
// Additional headers
$headers .= 'To: Bob <$to>, Bob <$to>' . "'r'n";
$headers .= 'From: Website <noreply@example.com>' . "'r'n";
$headers .= 'Cc: noreplt@example.com' . "'r'n";
$headers .= 'Bcc: noreply@example.com' . "'r'n";
if ($_POST['send']){
mail($to, $subject, $body, $header);
echo 'Message Sent.';
} else {
die('Failed to Send');
}
?>
使用mail($to, $subject, $body, $headers);在这里你用了$header