<?xml version='1.0'?>
<rss version='2.0'>
<channel>
<title>The New Forest Guardian</title>
<link>http://newforestguardian.com/index.php</link>
<description>The New Forest Guardian - Your top local source of
info for the New Forest area </description>
<item>
<title>Open Mapping comes to the New Forest</title>
<link>http://newforestguardian.com/nfgstory.php?id=2 </link>
<description>This weekend several volunteers from all over the
world descend on the New Forest to create a new, copyright-free
digital map.</description>
<pubDate>Fri, 22 Sep 2006 12:00:00 GMT</pubDate>
</item>
<item>
<title>Killer Pig on the Loose !!!!!;/title>
<link>http://newforestguardian.com/nfgstory.php?id=1 </link>
<description>Man-eating pig attacks New Forest villagers
</description>
<pubDate>Fri, 22 Sep 2006 12:30:00 GMT</pubDate>
</item>
</channel>
</rss>
Explanation of example
A channel is an RSS feed relating to one particular topic,
in this case, news items in the New Forest provided by the New Forest Guardian
website
The channel has three important tags describing it:
title - the title of the feed
link - the address of the feed
description - a description of the feed
The channel then has a number of individual items (e.g.
stories)
Each item has a:
title - e.g. a headline
link - URL where you can find out more
description - a short description of the item
pubDate - the date of publication, you can use this to
select the latest items
How is an RSS feed generated?
Imagine you wanted to create an RSS feed of updates to your website...
how would you do this?
On a very basic level, you create the RSS XML file on your server and
publish its URL
People can then subscribe to the feed by entering the URL into
news-reading software (see below)
However this has one obvious disadvantage.. the XML would have to
be manually updated each time you wanted to send out a new item!
Auto-generation of RSS feeds
Another possibility is to generate RSS feeds dynamically
using server-side scripting, e.g. PHP
For example, if you were running a news site, you could generate the
feed by querying the database for the latest stories
Code example:
<?php
header("Content-type: application/rss+xml");
$conn=mysql_connect("localhost","username","password");
mysql_select_db("database");
// Order articles most recent first
$result=mysql_query("SELECT * FROM stories ORDER BY pubDate DESC");
echo "<rss version='2.0'>";
echo "<channel>";
echo "<title>New Forest Guardian</title>";
echo "<link>http://newforestguardian.com/rss.php</link>";
echo "<description>Latest stories from the NFG</description>";
while($row=mysql_fetch_array($result))
{
echo "<item>";
echo "<title>$row[title]</title>";
echo "<link>http://newforestguardian.com/newsitem.php?id=$row[ID]</link>";
echo "<description>$row[description]</description>";
// This line converts a database date format
// (e.g. 2006-09-22 12:30:00) to an RSS date
// (e.g. Fri, 22 Sep 2006 12:30:00 GMT)
$rssdate = date("D, j M Y H:i:s", strtotime($row["pubDate"])). " GMT";
echo "<pubDate>$rssdate</pubDate>";
echo "</item>";
}
echo "</channel>";
echo "</rss>";
mysql_close($conn);
?>
Note how the contents of each RSS tag are based on the database
Also note how the link tag contains a link to the full story;
we do this by linking to another script, newsitem.php, and passing
it the ID of the story as a query string
RSS and Blogs
The newest use of RSS is in association with blogs
Blogs (weblogs) are basically online "diaries", frequently updated
by their author, and used to publish all manner of things from progress on
a project to random thoughts, ideas and opinions - to which readers can
respond
To do your own blog, you install blogging software such as Wordpress on
your web server
Blogging software automatically creates RSS feeds of each blog entry
Thus people can subscribe to your blog - and be informed of the latest
entries - by subscribing to its RSS feed
Subscribing to an RSS feed
There are a number of ways to subscribe to an RSS feed:
If you then enter a website address (e.g. www.free-map.org.uk)
in a newsreader, it will find the RSS feed automatically
Integrating RSS feeds into other websites
With a bit of scripting, it is possible to integrate a RSS feed made by
someone else into your own website
e.g. on free-map.org.uk I might want to include the blog entries at
www.opengeodata.org
There are libraries available for reading RSS, e.g. for PHP:
MagpieRSS
This would work by:
PHP script on your website requests RSS feed from another site
RSS sent back to your site
PHP reads the RSS and displays links to (and perhaps descriptions of)
the articles
GeoRSS
GeoRSS is a variant of RSS optimised for geographical data, such as
points of interest. A GeoRSS feed can be generated from a database of points of
interest, in a similar way that a regular RSS feed can be generated from a
database of news stories. GeoRSS can then be integrated into online mapping
applications using JavaScript mapping libraries, such as those used in
Google Maps or OpenStreetMap.
Here is an example of some GeoRSS. It is based on the Atom
variant of RSS rather than RSS 2.0. Note how a combination of ordinary RSS
(Atom) tags and extensions (beginning with georss:) are present.
The
extensions include:
georss:point - the latitude and longitude of the point of
interest;
georss:featuretypetag - the type of feature that it is.
FeaturesThe Red LionNice pub on the village green25651 -1pubThe Crown InnDecent pub25750.99 -1.01pub
]]>
Exercises
Today's exercise is to create an RSS feed for
THE PEOPLE'S PAPER, a well-known daily newspaper.
THE PEOPLE'S PAPER website has already been started in this
ZIP file; the
following pages are present:
the index page (index.php);
the page to display the full details of a
story (fullstory.php);
a page to allow a user to enter a story (addstory.html).
Upload these existing pages to your space
on Edward. If you login to PHPMyAdmin (
http://edward/phpmyadmin)
you will see a table called stories; you will be working with this.
Write a script to generate an RSS feed from the stories
table. Look at the RSS-generating example above for
guidance. Each entry in the feed
should link to the full story for that entry, by linking to
fullstory.php and
provide the story ID as a query string).
Add the 'link rel=alternate...'
line to the index page, to link the index page to the RSS feed,
so that the RSS icon will appear when the user visits the site.
The ZIP file also contains a form to add a new story (addstory.html).
Write a PHP script to respond to this form and to add the story
into the database. (Finish in your own time
if necessary) . One of the fields in the database is 'dateadded', you
can use the inbuilt MySQL function
NOW() to get the current time e.g.
mysql_query("INSERT INTO table (column1,column2,dateadded) VALUES
('$x','$y',NOW())");
Test it out by visiting the index page and subscribing to the feed.
