10.3. Generating the RSS

Really Simple Syndication (RSS) is an easy way to notify others of content changes. RSS feeds are used to publicize new blog posts, news events, new product additions to e-commerce sites and more. Visitors typically will subscribe to a feed you make available and are then able to automatically review updates directly from within their favorite aggregator without having to visit the site in a browser.

For historical reasons there are several different RSS formats. They are all XML-based although they aren't necessarily compatible with one another. I've chosen RSS 2.0 to publicize the new posts.

The root element of the feed is rss. Information about the site is placed in a channel section using title, link, and description elements. Any number of item elements follow the channel section, one for each post you want to publicize, each with title, link, and description elements.

Here is public_files/rss.php:

<?php header('Content-Type: text/xml'), ?>
<?xml version="1.0"?>
<rss version="2.0">
<channel>
  <title>My Blog</title>
  <link>http://www.example.com/myBlog</link>
  <description>
   My Blog is a place where I write my innermost thoughts and feelings for
   all the world to read.
  </description>
 </channel>
<?php
// include the 5 most recent entries
$query = sprintf('SELECT POST_ID, POST_TITLE, POST_TEXT, ' .
    'UNIX_TIMESTAMP(POST_DATE) AS POST_DATE FROM %sBLOG_POST ' .
    'ORDER BY POST_DATE DESC', DB_TBL_PREFIX);
$result = mysql_query($query, $GLOBALS['DB']);

$count = 0;
while (($row = mysql_fetch_array($result)) && $count++ < 5)
{
    echo '<item>';
    echo '<title>' . htmlspecialchars($row['POST_TITLE']) . '</title>';
    printf('<link>http://www.example.com/myBlog/view.php?m=%d&y=%d</link>',
        date('n', $row['POST_DATE']), date('Y', $row['POST_DATE']));
    echo '<description>' . htmlspecialchars($row['POST_TEXT']) . '</description>';
    echo '</item>';
}
?>
</rss>

I've included only the required elements in my feed, but there are others you can include to provide more information. Table 10-1 shows a listing of all elements for the RSS 2.0 specification.

<rss version="2.0">
 <channel> ... </channel>
</rss>

<channel>
 <title>...</title>
<link>...</link>
 <description>
 ... </description>
<item> ... </item>
 <item> ... </item>
 ...
</channel>

<item>
 <title>...</title>
<link>...</link>
 <description>
 ...
 </description>
</item>

<category domain="syndic8">
 Web Log</category>

<cloud domain="www.example.com
"port="80" path="/RPC" protocol="xml-rpc"
 registerProcedure="NotifyMe" />

<copyright>
 Copyright 2007
</copyright>

<description>
 My Blog is a place where I write my
innermost thoughts and feelings for all the world to read.
</description>

<docs>
 http://blogs.law.harvard.edu/tech/rss
</docs>

<generator>PHP</generator>

<image>
 <url>
http://www.example.com/img/logo.png
 </url>
 <title>My Blog</title>
<link>http://www.example.com</link>
</image>

<language>en-us</language>

<pubDate>
Wed, 21 Nov 2007 21:55:00 EST
</pubDate>

<link>http://www.example.com</link>

<managingEditor>
 [email protected]
</managingEditor>

<pubDate>
 Wed, 21 Nov 2007 21:55:00 EST
</pubDate>

<rating>
 (PICS-1.1 "http://www.classify.org/
safesurf/" L  gen true for "http://www
.example.com"  r (SS~~000 6 SS~~001 2
SS~~002 2 SS~~003 2 SS~~004 2 SS~~005 1
SS~~009 1))
</rating>

<skipDays>Saturday</skipDays>

<skipHours>0</skipHours>

<title>My Blog</title>

<ttl>120</ttl>

<webMaster>
 [email protected]
</webMaster>

<author>
 [email protected]
</author>

<category domain="syndic8">
 Web Log</category>

<comments>
http://www.example.com/comments.php
</comments>

<description>
 Once upon a time...
</description>

<enclosure url="http://www.example.com/
vid.mov" length="659435" type="video/
quicktime" />

<guid>
http://www.example.com/item123456
</guid>

<link>
http://www.example.com/view.php?m=11&
y=2007
</link>

<pubDate>
 Wed, 21 Nov 2007 21:55:00 EST
</pubDate>

<source url="http://example.org">
example.org</source>

<title>
 My First Blog Entry
</title>