Creating RSS 2.0 Feeds - Caching and saving
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One advantage that the FeedCreator class has over Perl's XML::RSS is the built-in caching mechanism. PHP is mostly used, in this case, as a way of dynamically building a feed upon request, perhaps from a database. However, when a feed gets too popular, that might cause too much of a server load. You can have your script store a cache file and serve that instead of running itself by adding this line:
$rss->useCached();
This saves the dynamically created feed to a cache, serving that instead if it is less than one hour old. Remember, you need to place this line right underneath the $rss = new UniversalFeedCreator(); , or you'll waste precious processor cycles.
You can also explicitly save the file with a command like this:
echo $rss->saveFeed("RSS2.0", "index.xml");
Dates
Because, caching not withstanding, the feeds are usually produced dynamically, FeedCreator declares the channel/lastBuildDate element automatically at the time of creation. You can, of course, specify it explicitly, as you can with pubDate. FeedCreator allows the use of RFC 822 (Mon, 20 Jan 03 18:05:41 +0400), ISO 8601 (2003-01-20T18:05:41+04:00), and Unix (1043082341) time values.
Namespaced modules
This is the major drawback with the class. You can't, as of Version 1.71 at least, create a feed with modules in it. If you're set on doing that--perhaps with some groovy special in-house application in mind--you'll need to hack at the class's code. It is licensed under the GPL, so go right ahead.
Creating RSS 2.0 with Ruby
Since Version 1.8.2, Ruby has shipped with Kouhei Sutou's RSS parsing and creation library. At time of writing, however, Ruby has only reached 1.8.2.preview.3, and documentation is hard to come by. The only documentation for the new RSS classes is found at:
http://www.cozmixng.org/~rwiki/?cmd=view;name=RSS+Parser%3A%3ATutorial.en
in a potentially unreliable translation from the Japanese original.
Having said that, the library does seem very complete indeed, with support for the parsing and writing of both RSS 1.0 and 2.0. At time of writing, the tutorial just mentioned was growing rapidly and being completed by the library's author. Ruby programmers should check the URL for changes.
Serving RSS 2.0
Although, or perhaps because, there is no official word within the specification regarding this, the growing standard for serving RSS 2.0 is with a MIME type of application/xml. Dave Winer prefers text/xml for the way that it causes the file to display itself nicely inside Internet Explorer. Using application/xml is more correct, but it causes browsers to download the file instead of displaying it. Really advanced users are looking at application/rss+xml, but currently no standard exists. It's up to you, but certainly, it should not be served with any other MIME type. text/plain is right out.
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 This article is excerpted from chapter four of the book Developing Feeds with RSS and Atom, written by Ben Hammersley (O'Reilly; ISBN: 0596008813). Check it out today at your favorite bookstore. Buy this book now.
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