Blue Anvil Journal » Blog Archive » Wordpress development techniques #2

Wordpress development techniques #2 - Fetching RSS feeds with wordpress

As promised last week, this week we are looking at fetching RSS feeds with Magpie RSS.

Magpie is an PHP based RSS feed parser; I.E. It fetches RSS feeds to display in other places, which gives it many uses.

Unknown to many, wordpress has the magpie RSS parser built in, this article will teach you how to use it, and also how to fetch and show someones del.icio.us bookmarks!

Fetching feeds in wordpress

Wordpress contains two functions for fetching feeds:

fetch_rss -This function fetches and parses an RSS feed.
wp_rss - This function fetches and parses an RSS feed, then displays the results in an unordered list.

These functions use magpie for parsing the RSS, and Snoopy for retrieving the RSS.

Uses the MagpieRSS and RSSCache (http://magpierss.sourceforge.net/) functions for parsing and automatic caching and the Snoopy HTTP client (http://sourceforge.net/projects/snoopy/) for the actual retrieval.

Including Magpie in a template or plug in

Magpie RSS is built into wordpress’ rss-functions.php file (or rss.php in newer versions). It contains the functions needed to fetch feeds, so it needs to first be included:

1
2

// Include the RSS functions. Older versions of wordpress could use include_once (ABSPATH . WPINC . '/rss-functions.php') or include_once (ABSPATH . WPINC . '/rss.php');;
include_once(ABSPATH . WPINC . '/rss-functions.php');

Fetching the feed with fetch_rss

Next lets tell wordpress what feed we want to parse, and put it to work! If you want to get the results and output them yourself, use fetch_rss.

1 2	// Fetch a feed $feed = fetch_rss("http://yourfeedaddress");

To limit you results you can slice the array of results:

1	$items = array_slice($feed->items, 0, $maxitems);

After that, use a loop to go through the array contents and output the results (see the del.icio.us bookmarks example further down for more detail on this).

Fetching the feed with wp_rss

If you want to output the results in an unordered list right away, use wp_rss.

1 2	// Fetch a feed, replace $limit with the max results you want wp_rss("http://yourfeedaddress", $limit);

Example output

The below example shows output from my bookmarks feed using wp_rss.

include_once(ABSPATH . WPINC . ‘/rss-functions.php’);
wp_rss(’http://del.icio.us/rss/mikejolley’, 5);

Fetching del.icio.us bookmarks - example

The following code gets my last 5 del.icio.us bookmarks, and outputs them to the page.

<?php
	// Include the RSS functions of wordpress
	include_once(ABSPATH . WPINC . '/rss-functions.php')
	// Grab my RSS feed
	$feed = fetch_rss("http://del.icio.us/rss/mikejolley");
        // I want 5 results please
	$maxitems = 5;
	$items = array_slice($feed->items, 0, $maxitems);
        // Output the results!
	if(!empty($items)) {
		echo '<ul>';
		foreach ($items as $item) {
			echo '<li>';
			echo '<a href="';
                        // This is a bit messy, but it makes the output valid XHTML strict by removing ampersands
			$item['link'] = str_replace("&", "&amp;", $item['link']);
			$item['link'] = str_replace("&amp;&amp;", "&amp;", $item['link']);
                        // End of messyness. Output the link
			echo $item['link'];
			echo '">';
                        // Output the title
			echo $item['title'];
			echo '</a>';
                        // If i've written a description, output it
			if (isset($item['description'])) {
			        echo '<br />';
				echo $item['description'];
			}
			echo '</li>';
		}
		echo '</ul>';
	}
?>

Neat huh? See what it outputs below:

$feed = fetch_rss(”http://del.icio.us/rss/mikejolley”);
$maxitems = 5;
$items = array_slice($feed->items, 0, $maxitems);
if(!empty($items)) {
echo ‘

‘;
echo ‘

1	define("MAGPIE_OUTPUT_ENCODING", "UTF-8");

That line of code simply sets the output of the fetched feed to be in UTF-8 encoding. Handy.

More about wordpress rss functions

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5 - Lakshmi Mareddy says:

Pretty cool Mike! or should I say “Jolley Good”… I had played with Magpie separately long back, but didnt know it was built-in in WP. Now after reading your article, my mind is racing… A big THANK YOU to you for coming up with this…

Comment made on September 22, 2007 at 10:52 pm

6 - Christopher Miles says:

Thanks a lot for this post; I’m now using the native RSS fetcher in Wordpress to create a blogroll on my site using del.icio.us links, and a current and recent reading list from my Google Library RSS feed

I’m spending half my waking day thinking of new and fiendish ways of parsing RSS feeds to my site now!

(”Half my waking day” and “fiendish” are probably overstating it a bit.)

Comment made on November 20, 2007 at 2:38 pm

7 - Mark says:

Your lesson is similar to one I found on the wordpress codex but yours is more detailed. I have one question: Do you know if there is a way to display/echo the pubdate for each item? I have not been able to figure that out.

Thanks!

Comment made on December 14, 2007 at 11:07 pm

8 - WordPress Plugins Database » Plugin Details » aggr says:

[...] aggr allows you to place the contents of an RSS feed into your pages or posts. It is a deeply modified version of the Aggregate plugin of Rob Miller (I also used an idea of Michael Jolley). [...]

Pingback made on January 5, 2008 at 8:37 am

9 - Feedburn your delicious rss feeds! | nemetral says:

[...] a nice how-to on Blue Anvil Journal, but you may see an error happening right in the [...]

Pingback made on April 23, 2008 at 1:02 pm

10 - Steve says:

Is it just me, or does anyone else see, “Warning: array_slice() [function.array-slice]: The first argument should be an array in /home/sites/blue-anvil.com/public_html/wp-content/plugins/phpexec.php(41) : eval()’d code on line 4″, in the example boxes? The only reason I ask, is because I am getting this error too, when I try to parse a feed from my own website. It works the first time, but then on refresh it dies and give me a similar error.

Comment made on May 7, 2008 at 4:59 pm