Thanks to the hard work of Dr. Mike, users of WordPressMU have found a solution for implementing site-wide tags and searching without significant changes to the WordPressMU or WordPress core code bases. The basic idea behind the most popular solution is to make an instances of WordPress (classic) that stores a mirror of your WordPressMU sitewide feed. I won’t go into details explaining how this is done, because there is a very clear and well documented process found here in the WordPressMU forums.
I’ve used this solution and it appears to work very well, and is actually very easy to implement. It took me about an hour when I first set it up.
However, in the process of sharpening my wordpress skill, I wanted to learn a little bit more about filters and actions. After seeing what some other people have done with filters, I’m pretty much convinced that if you know the right filter to add, you can probably implement almost anything without making core changes. So, I wanted to try to build a solution that allows you to use Dr. Mike’s cool workaround without making any changes to the wordpress core code. This plugin does that.
Actually, it’s really simply, it just adds a “post_link” filter that returns the $post->guid as the permalink. This is essentially the same thing that was being done by the change to “link-template.php” that Dr. Mike’s instructions say to do for step 6.
Download: You can get a copy of the plugin here.
Install: Standard stuff, rename the file to .php, place it in your plugins directory (in this case on your wordpress install, not on your wordpressmu install) and activate it. After you have it installed you can revert your changes to “link-template.php” back to the original.
Usage: nothing special to do.