Wordpress数据已插入数据库，但无法在页面中显示成功消息，并在控制台中显示错误

Question

我正在研究自定义的wordpress主题，我尝试使用ajax提交联系表单。我正确地完成了所有操作，并且数据正在插入数据库中，但是无法在html中打印成功消息，并且在控制台中也出现了错误，例如admin-ajax.php bad 400，但是当我单击它时，它显示了消息状态1。

<div class="container">

              <h2 class="text-center"> Submit Your Query</h2>
              <div class="text-center messageDiv" style="color:#fff">

              </div>
            <form action="" method="post" id="myform">

            <!-- Form start -->
             <div class="row">
                <!-- Name -->
               <div class="col-lg-4 col-12">
                <div class="form-group">
                 <label>Name</label>
                 <input type="text" name="name" class="form-control" required>
                </div>
               </div>
               <!-- Email -->
               <div class="col-lg-4 col-12">
                <div class="form-group">
                 <label>Email</label>
                 <input type="email" name="email" class="form-control"  required>
                </div>                  
               </div>
               <!-- Phone -->
               <div class="col-lg-4 col-12">
                <div class="form-group">
                 <label>Phone</label>
                 <input type="text" name="phone"  class="form-control">
                </div>                  
               </div>
               <!-- Subject -->
               <div class="col-lg-12 col-12">
                <div class="form-group">
                 <label>Subject</label>
                 <input type="text" name="subject" class="form-control"  required>
                </div>                  
               </div>
               <!-- Message -->
               <div class="col-lg-12 col-12">
                <div class="form-group">
                 <label>Message</label>
                 <textarea class="form-control" rows="5" name="feedback" required></textarea>
                </div>                  
               </div>
               <!-- Submit button -->
               <div class="form-group mx-auto">
                <button class="cutombtn-form" name="submit-form">SUBMIT</button>
               </div>
               </div>
             </form>             
            </div>

           </div>
        </div>
      </div>
    </div> 

jQuery

<script>
       jQuery(function(){

           var ajaxurl = '<?php echo admin_url('admin-ajax.php'); ?>';

           jQuery('#myform').submit(function(e){
             e.preventDefault();
             jQuery.ajax({
                 dataType: 'json',
                 type: "post",
                 data: jQuery("#myform").serialize(),
                 url: ajaxurl,
                 success:function(data){
                     jQuery('.messageDiv').html(data.message);
                 }
             });
           });
       });
    </script>

function.php

if(isset($_POST['name'])){
   global $wpdb;
     $data_array=array(
         'name'       => $_POST['name'],
         'email'      => $_POST['email'], 
         'phone'      => $_POST['phone'],
         'subject'    => $_POST['subject'],
         'message'    => $_POST['feedback']
     );

   $table_name= 'form_entry';
   $row_result = $wpdb->insert($table_name, $data_array, $format=NULL);

   //result of form
   if($row_result == 1){

      echo json_encode(array('message' => 'Form Submitted successfully','status' => 1)) ;
   }
    else{
      echo json_encode(array('message' => 'Unable to submit the form.','status' => 0)) ;
   }
}