如何从ajax中获取php的变量messageID？

Question

Need some help!!! it's web message system. I click on the button to make ajax call to return data and a popup comes on the screen where users can message other users. Then I have a getMessages function to retrieve data to display the conversation if exists inside div class chat-box-body. Problem is: On the data returned I have php echoing messageID on input submit #send data-message="messageID", and I need get this value from php to make another ajax call get constantly update on the conversation every 2 sec. any help would be too much appreciated!!! thank you!

  message.js file

 $(document).on('click', '#directMsg', function(){
        user_id   = $(this).data('user');

        $.post('http://localhost/core/ajax/messages.php', {directChatBox:user_id}, function(data) {

              $('.popup-kamppo').html(data);

              messageID = $(this).data('message');
              //lastInsertMsg = '';

              });

              // Function to refresh the chatbox every five seconds
              getMessages = function() {
                    //user_id   = $(this).data('user');
                    messageID = $(this).data('message');
                    //lastInsertMsg = '';

                    if (messageID == '' || messageID == 0) {
                          messageID = lastInsertMsg;
                    } else {
                          messageID = messageID;
                    }
                    $.post('http://localhost/core/ajax/messages.php', {updateChatBox:messageID}, function(data) {
                          $('.chat-box-body').html(data);

                    });

              }
             // timer = setInterval(getMessages, 10000);
              getMessages();

        });

        $('.close-popup-onclick').click(function(){
              clearInterval(timer);
              $('.chat-box').hide();
        });

  });



 message.php jax file

 if (isset($_POST['directChatBox']) && !empty($_POST['directChatBox'])) {
  $user_id   = $_SESSION['user_id'];
  $messageTo = $_POST['directChatBox'];
  $message   = $messageObj->checkDirectConversation($user_id, $messageTo);

  $user        = $getFromUser->userData($user_id);
  ?>
  <div class="chat-box">
        <div class="chat-box-wrapper">
              <div class="chat-box-inner">
                    <div class="chat-box-h">
                          <label class="l-left" for="message-send">
                                <span  class="message-close-arrow"><i class="fa fa-chevron-left" aria-hidden="true"></i></span>
                          </label>
                          <div  class="chat-box-title">
                                <div class="chat-box-img">
                                      <img src="<?php echo BASE_URL.$user->profile_image; ?>">
                                </div>
                                <span>Mensagens</span>
                          </div>
                          <label class="l-right">
                                <span class="message-close-popup"><i class="fa fa-times close-popup-onclick" aria-hidden="true"></i></span>
                          </label>

                    </div>
                    <div class="chat-confirmation-box">
                          <h3>Voce tem certeza que deseja apagar esta mensagem??</h3>
                          <button class="cancel-del" value="cancel-del">cancelar</button>
                          <button class="del-msg" value="del-msg">Apagar</button>
                    </div>
                    <div id="chatBox" class="chat-box-body">

                    </div>
                    <div class="main-msg-footer">
                          <div class="main-msg-footer-inner">
                                <ul>
                                      <li><textarea id="msg" name="msg" placeholder="Mande a sua mensagem!"></textarea></li>
                                      <li><input id="msg-upload" type="file" value="upload"/><label for="msg-upload"><i class="fa fa-camera" aria-hidden="true"></i></label></li>
                                      <li><input id="send" type="submit" value="Enviar" data-user="<?php echo $messageTo; ?>" data-message="<?php echo $message->messageID;  ?>"/></li>
                                </ul>
                          </div>
                    </div>
              </div>
        </div>
  </div>
  <?php
 }