Tip: Combining multiple blogs into a single feed

I will be using Movable Type's default RSS 2.0 template, simply for size reasons. These template changes can apply just as easily to Atom feeds or any other feed template you can come up with.

First, here is the default template:

<?xml version="1.0" encoding="<$MTPublishCharset$>"?>
<rss version="2.0">
   <channel>
      <title><$MTBlogName remove_html="1" encode_xml="1"$></title>
      <link><$MTBlogURL$></link>
      <description><$MTBlogDescription remove_html="1" encode_xml="1"$></description>
      <language><$MTBlogLanguage ietf="1"$></language>
      <copyright>Copyright <$MTDate format="%Y"$></copyright>
      <lastBuildDate><MTEntries lastn="1"><$MTEntryDate format_name="rfc822"$></MTEntries></lastBuildDate>
      <generator>http://www.sixapart.com/movabletype/?v=<$MTVersion$></generator>
      <docs>http://blogs.law.harvard.edu/tech/rss</docs>

      <MTEntries lastn="15">
      <item>
         <title><$MTEntryTitle remove_html="1" encode_xml="1"$></title>
         <description><$MTEntryBody encode_xml="1"$></description>
         <link><$MTEntryPermalink encode_xml="1"$></link>
         <guid><$MTEntryPermalink encode_xml="1"$></guid>
         <category><$MTEntryCategory remove_html="1" encode_xml="1"$></category>
         <pubDate><$MTEntryDate format_name="rfc822"$></pubDate>
      </item>
      </MTEntries>
   </channel>
</rss>

Next, we will substitute MTMultiBlogEntries for MTEntries. This will get the last 15 entries from the combined entry list of all of the included blogs. There are a number of options that will be available in the next major release of MultiBlog, but for now we will simply make use of the include_blogs attribute. In this example, the ids of the three blogs we wish to integrate will be 7, 21, and 24.

The blog ids can be retreived simply by going to the main menu for the particular blog and making note of the blog_id parameter in the URL.

Here are the modified portions of the template:

      <lastBuildDate><MTMultiBlogEntries include_blogs="7,21,24" lastn="1"><$MTEntryDate format_name="rfc822"$></MTMultiBlogEntries></lastBuildDate>

      <MTMultiBlogEntries include_blogs="7,21,24" lastn="15">
      <item>
         <title><$MTEntryTitle remove_html="1" encode_xml="1"$></title>
         <description><$MTEntryBody encode_xml="1"$></description>
         <link><$MTEntryPermalink encode_xml="1"$></link>
         <guid><$MTEntryPermalink encode_xml="1"$></guid>
         <category><$MTEntryCategory remove_html="1" encode_xml="1"$></category>
         <pubDate><$MTEntryDate format_name="rfc822"$></pubDate>
      </item>
      </MTMultiBlogEntries>

That's it!

For bonus points, let's add some information to the feed. We will add the blog name to the entry title so that entries from the different blogs can be distinguished.

<title><$MTBlogName remove_html="1" encode_xml="1"$>: <$MTEntryTitle remove_html="1" encode_xml="1"$></title>

Or, if you only want entries that are not from the current blog to have the blog names prepended to the titles:

<title><MTMultiBlogIfNotLocalBlog><$MTBlogName remove_html="1" encode_xml="1"$>: </MTMultiBlogIfNotLocalBlog><$MTEntryTitle remove_html="1" encode_xml="1"$></title>

If there are any other integration issues I can address, please let me know.