How do I find the number of ACTIVE MEMBERS on a forum?

I am putting together a Forum Stats website and I need to find the number of Active M开发者_JAVA百科embers on several forums.

Many have "Total members" listed but that doesn't help me.

I'm considering "Active" as someone that has posted at least 5 times within 6 the last months.

I'm really perplexed as to how this might be done. Any suggestions?

---

If you don't have access to the database, scraping the html pages, following links, and determining post-date & post-user from the HTML itself seems to only way to gp. (HTTPRequest or cURL for fetching, in combination with DOMDocument / DOMXpath for reliable HTML parsing & finding explicit nodes), storing it in your own database. All in all, depending on the exact HTML layout of the forums, not exactly complicated, but a lot of work, and possibly work you have to repeat again and again with small variations for each different forum.

If the forums have RSS feeds or other means of getting more structured content / data the amount of work needed could be greatly reduced.