按值简单的html dom解析器查找元素

Question

我需要通过现有值找到元素，我使用简单的html dom解析器，输入html - 可能不完整。 例 HTML：

<div class="params">
   <dl class="row param">
      <dt class="param_title">Name</dt>
      <dd class="param_content">Some name</dd>
   </dl>
   <dl class="row param">
      <dt class="param_title">Sum</dt>
      <dd class="param_content">23400</dd>
   </dl>
   <dl class="row param">
      <dt class="param_title">Address</dt>
      <dd class="param_content">Here some address</dd>
   </dl>
</div>
<div class="params">
   <dl class="row param">
      <dt class="param_title">Name</dt>
      <dd class="param_content">Some name</dd>
   </dl>
   <dl class="row param">
      <dt class="param_title">Address</dt>
      <dd class="param_content">Here some address</dd>
   </dl>
</div>

PHP：

foreach($html->find('dd[class=param_content]') as $el)
  echo $el->innertext . '<hr>';

结果：

Some name
23400
Here some address
-----------------
Some name
Here some address

但是这段代码对我不起作用，我需要输出这样的文字：

Some name
23400
Here some address
-----------------
Some name
Null<-because there is no Sum, write Null, that's what I'm looking for
Here some address