提交表单后的空白页

Question

我不知道发生了什么，但提交表单后我得到了空白页。 File 负责将我的网站与 Mailchimp 集成。下面我也分享html代码。我查看了变量，理论上在 php 和 html 文件中一切都是正确的。 API 密钥正确，MailChimp 的邮件列表编号也是正确的。什么可能导致这种情况？

<?php 
session_start();
if(isset($_POST['submit'])) {
    $email = $_POST['email'];
    if(!empty($email) && !filter_var($email, FILTER_VALIDATE_EMAIL)) === false) {
        //Mailchimp API credentials
        $apiKey = 'xxxxxxxxxxxxxx';
        $listID = 'xxxxxxxxxx';

        //Mailchimp API URL 
        $memberID = md5(strtolower($email));
        $dataCenter = substr($apiKey,strpos($apiKey,'-')+1);
        $url = 'https://' . $dataCenter . 'api.mailchimp.com/3.0/lists?fields=' . $listID . '/members' . $memberID;

        // member information

        $json = json_encode ([
            'email_address' => $email,
            'status' => 'subscribed',
        ]);

         // send a HTTP POST request with curl
         $ch = curl_init($url);
         curl_setopt($ch, CURLOPT_USERPWD, 'user:' . $apiKey);
         curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
         curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
         curl_setopt($ch, CURLOPT_TIMEOUT, 10);
         curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT');
         curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
         curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
         $result = curl_exec($ch);
         $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
         curl_close($ch);
         
         // store the status message based on response code
         if ($httpCode == 200) {
             $_SESSION['msg'] = '<p style="color: #34A853">You have successfully subscribed to CodexWorld.</p>';
         } else {
             switch ($httpCode) {
                 case 214:
                     $msg = 'You are already subscribed.';
                     break;
                 default:
                     $msg = 'Some problem occurred, please try again.';
                     break;
             }
             $_SESSION['msg'] = '<p style="color: #EA4335">'.$msg.'</p>';
         }
     }else{
         $_SESSION['msg'] = '<p style="color: #EA4335">Please enter valid email address.</p>';
     }
 }
 // redirect to homepage
 header('location:index.php');
    }
}

<!-- Modal Newsletter Start-->
<div id="myModal" class="modal fade">
    <div class="modal-dialog modal-newsletter">
        <div class="modal-content">
            <?php echo $statusMsg: ?>
            <form method="post" action="action.php">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-hidden="true"><span>&times;</span></button>
                </div>
                <div class="modal-body text-center">
                    <h4>Subscribe to our newsletter</h4>
                    <p>Signup to our weekly newsletters to get the latest news, updates and amazing offers!</p>
                </div>
                <div class="input-group">
                    <input type="text" name="email" class="form-control" id="emapleInputEmail1" placeholder="Enter your email..." required>
                    <input type="submit" name="submit" class="btn btn-primary" value="Subscribe">
                </div>
            </form>
        </div>
    </div>
</div>