Getting recent posts from all blogs on mother blog - multisite

Question

I want to get the recent comments on all posts in a multisite network, and I want to display these ceomments in a sidebar on the multisites "mother" blog. To complicate: All blogs are forced to post in either category A or category B. I want two outputs on the mother blog, showing comments on posts in category A and a second output for comments posted in category B. Question: Is this possible?

Answer 1

Well it is quite possible, when using a multisite you have a few extra tables in your database. One of them is one that is called wp_site which has inside it a list of all your blogs. It looks something like

site_id | blog_id | some other vars ...
1         1         ...
1         2         ...
1         3         ...

You would have to fetch all of these, and then you could fetch all other posts comments using the $wpdb->get_results more or less like so,

foreach ($blogs as $blog) {
  $blog_comments = $wpdb->get_results("SELECT c.*, p.* FROM wp_{$blog->blog_id}_comments AS c INNER JOIN wp_{$blog->blog_id}_posts AS p ON c.comment_post_ID = p.ID ORDER BY comment_date DESC LIMIT 0,10"); // Get the latest 10 comments from each blog and it's related post
}

Afterwards you would need to check for the posts category and post it on the front side accordingly.

If you need more help, comment here, I'll try to supply more data.

Answer 2

There are quite a bit of plugins available to do this for you, a quick Google search will get you there.

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Bloglist, recent posts and comments from the whole network.

Can be found here.

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A central area where all the posts on a WordPress MU or WordPress MS site can be collected.

Can be found here.

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A list of premium plugins (one matching your exact requirement) can be found here.
There are quite a bit more, free and premium, but I can only add some many links to this answer.

Hope this helps,