PHP邮件不显示文本危险警报，提交时也会转到空白页

我的网站上的PHP联系人表单模式正在发送电子邮件，但如果字段为空，或者在验证某人是否为人类时输入了错误的数字，它不会显示错误消息。此外，单击"提交"后，它将转到一个空白页面。

这是我的HTML文件：

<!-- Modal -->
<div id="contactModal" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="contactModalLabel" aria-hidden="true">
  <div class="modal-dialog modal-lg">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
        <h4 class="modal-title">Fill everything out below!</h4>
      </div>
      <div class="modal-body">
        <div class="container-fluid">
          <div class="row">
            <div class="col-xs-12 col-sm-10 col-sm-offset-1">
              <form class="form-horizontal" role="form" method="post" action="mailer.php">
                <div class="form-group">
                  <label for="name" class="col-sm-2 control-label">Name</label>
                  <div class="col-sm-10">
                    <input type="text" class="form-control" id="name" name="name" placeholder="First & Last Name" value="<?php echo htmlspecialchars($_POST['name']); ?>">
                    <?php echo "<p class='text-danger'>$errName</p>";?>
                  </div>
                </div>
                <div class="form-group">
                  <label for="email" class="col-sm-2 control-label">Email</label>
                  <div class="col-sm-10">
                    <input type="email" class="form-control" id="email" name="email" placeholder="example@domain.com" value="<?php echo htmlspecialchars($_POST['email']); ?>">
                    <?php echo "<p class='text-danger'>$errEmail</p>";?>
                  </div>
                </div>
                <div class="form-group">
                  <label for="message" class="col-sm-2 control-label">Message</label>
                  <div class="col-sm-10">
                    <textarea class="form-control" rows="4" name="message">
                      <?php echo htmlspecialchars($_POST[ 'message']);?>
                    </textarea>
                    <?php echo "<p class='text-danger'>$errMessage</p>";?>
                  </div>
                </div>
                <div class="form-group">
                  <label for="human" class="col-sm-2 control-label">2 + 3 = ?</label>
                  <div class="col-sm-10">
                    <input type="text" class="form-control" id="human" name="human" placeholder="Your Answer">
                    <?php echo "<p class='text-danger'>$errHuman</p>";?>
                  </div>
                </div>
                <div class="form-group">
                  <div class="col-sm-10 col-sm-offset-2">
                    <input id="submit" name="submit" type="submit" value="Send" class="btn btn-primary">
                  </div>
                </div>
                <div class="form-group">
                  <div class="col-sm-10 col-sm-offset-2">
                    <?php echo $result; ?>
                  </div>
                </div>
              </form>
            </div>
          </div>
        </div>
      </div>
      <!-- End of Modal body -->
    </div>
    <!-- End of Modal content -->
  </div>
  <!-- End of Modal dialog -->
</div>
<!-- End of Modal -->

这是我的PHP文件：

<?php
	if (isset($_POST["submit"])) {
		$name = $_POST['name'];
		$email = $_POST['email'];
		$message = $_POST['message'];
		$human = intval($_POST['human']);
		$from = 'Contact Form'; 
		$to = 'myemail@gmail.com'; 
		$subject = 'Message from porfolio site ';
		
		$body = "From: $name'n E-Mail: $email'n Message:'n $message";
 
		// Check if name has been entered
		if (!$_POST['name']) {
			$errName = 'Please enter your name';
		}
		
		// Check if email has been entered and is valid
		if (!$_POST['email'] || !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
			$errEmail = 'Please enter a valid email address';
		}
		
		//Check if message has been entered
		if (!$_POST['message']) {
			$errMessage = 'Please enter your message';
		}
		//Check if simple anti-bot test is correct
		if ($human !== 5) {
			$errHuman = 'Your anti-spam is incorrect';
		}
 
// If there are no errors, send the email
if (!$errName && !$errEmail && !$errMessage && !$errHuman) {
	if (mail ($to, $subject, $body, $from)) {
		$result='<div class="alert alert-success">Thank You! I will be in touch</div>';
	} else {
		$result='<div class="alert alert-danger">Sorry there was an error sending your message. Please try again later</div>';
	}
}
	}
?>

你们知道这里会发生什么吗？