wordcloud错误：没有输出文本，只有黑色背景

Question

我正试图弄个词云，我已经编写了代码。该代码未显示任何错误，但是，我在词云上未获得任何文本输出，屏幕只是空白，背景色

<table id="datatables" class="css-serial text-center table table-striped table-no-bordered table-hover dataTable dtr-inline">
  <thead>
      <tr role="row">
          <th>#</th>
          <th>Department</th>
          <th>Action</th>
      </tr>
  </thead>
  <tfoot>
      <tr>
          <th rowspan="1" colspan="1">#</th>
          <th rowspan="1" colspan="1">Department</th>
          <th rowspan="1" colspan="1">Action</th>
      </tr>
  </tfoot>
  <tbody>
      <?php foreach ($departments  as $key => $department) { ?>
          <tr>
              <td>
                  <p data-letters="<?php echo ucwords(substr($department['department'], 0, 1)); ?>"></p>
              </td>
              <td><?php echo $department['department'] ?></td>
              <td>
                  <button class='edit_department btn btn-danger btn-link' id='<?php echo $department['id'] ?>'><i class='material-icons'>edit</i></button>
                  <button class='delete_department btn btn-danger btn-link' id='<?php echo $department['id'] ?>'><i class='material-icons'>close</i></button>
              </td>
          </tr>
      <?php } ?>
  </tbody>
</table>

获得具有红色背景色的空白屏幕。没有文本。