當(dāng)用戶輸入他們的聯(lián)系方式并按下提交按鈕時(shí)，我的聯(lián)系表單不會(huì)發(fā)送電子郵件。我究竟做錯(cuò)了什么？HTML：    <div class="row">    <form action="mail.php" accept-charset="utf-8" method="post">    <div class="form-group contacts-form-result">    <div class="col-xs-12">    <strong></strong>        </div>    </div>    <div class="form-group clearfix">    <div class="col-xs-12 col-md-6">    <input type="text" placeholder="Your name *" name="name" class="form-control" required>    </div>    </div>    <div class="form-group clearfix">    <div class="col-xs-12 col-md-6">    <input type="email" placeholder="Your e-mail address *" name="email" class="form-control" required>    </div>    </div>    <div class="form-group clearfix">    <div class="col-xs-12">    <textarea placeholder="Your message *" rows="7" name="message" class="form-control" required></textarea>    </div>    </div>    <div class="form-group clearfix">    <div class="col-xs-12">    <button type="submit" class="btn btn-2">Send Enquiry</button>    </div>    </div>    </form>PHP：<?phpif (isset($_POST['submit'])){  $subject = $_POST['subject'];  $name = $_POST['name'];  $mailFrom = $_POST['email'];  $message = $_POST['message'];  $mailTo = "myemail@email.com";  $headers = "Enquiry from: ".$mailFrom;  $txt = "Name: ".$name."\n"."Message: ".$message;mail($mailTo, $subject, $txt, $headers); header("Location: success.html?mailsent");}?>我該如何解決這個(gè)問題，以便在按下按鈕時(shí)發(fā)送電子郵件？謝謝你。