每隔X个单词插入广告（或文字）wordpress - Wordpress

Question

我试图每300个单词插入广告块，所以如果帖子有250个单词，请不要显示任何宣传。

我现在使用这个标签（通过段落，但我需要它来处理单词/字符）：

<?php
  $content = apply_filters('the_content', $post->post_content);
  $save = explode("</p>", $content);
  $count = 0;
  foreach ($save as $a) {
    if ($count == 2) {
      echo "";
  ?>AD_3
<?php 
      echo "";
    } else if ($count == 3) {
      echo "</p><div>";
      ?>AD_1
<?php 
      echo "</div>";
    } else if ($count == 5) {
      echo "</p>";
      ?><?php 
      echo "";
    } else if ($count == 6) {
      echo "</p>";
      ?>AD_2<?php
      echo "";
    }
      echo $a."";
    $count = $count + 1;
  }
  ?>

我需要与此类似的东西（但我无法使其发挥作用）：insert text in content after 300 words but after the closing tag of a paragraph

有人可以帮助我吗？

谢谢！