在使用PHP正则表达式的字符串后查找以下x次出现？

I'd like to preg_match all div ids following the p tag with name="groups". How do I write this expression in PHP? (The html is malformed so I can't use XPath ...)

<p name="groups">
  <div id="55">fifty-five</div>
  <div id="65">sixty-five</div>
  <div id="75">seventy-five</div>
</p>

The ideal output would be something like:

  array
    55
    65
    75

  array
    fifty-five
    sixty-five
    seventy-five

Whilst using regex to parse html is usually not good, using it to match certain pieces of html for limited jobs can be fine.

Here's the regex:

<p name="groups">(\s*<div id="([0-9]+)">([a-z\-]+)</div>)+\s*</p>