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Saturday, March 14, 2009

Generating XML Feeds (RSS, Atom) Using PHP

RSS/ATOM feeds are very common these days and almost all Content Management Systems (CMS) can generate it. But in the case when you want to generate it yourself or just want to learn how you can, read on!

Both RSS and ATOM feeds are written in eXtensible Markup Language (XML) standard markup. Not just standard markups, you also need to be sure of what and how you put data in those markup elements (tags). For all this refer to the feed specifications of RSS and ATOM. XML itself is very strict and the standard specifications makes it even harder to generate valid feeds. And moreover, why re-invent the wheel when we can have it – ready-made.

The solution I'm referring to here is, to use a third-party Library – Universal FeedWriter. FeedWriter is a PHP class written by Anis uddin Ahmad that can dramatically  ease-off feeds (both RSS and Atom) generation. You can download this library from here.

Every feed should have at least the following data:

  1. Feed title
  2. URL(of the website whose feed is it)
  3. Description
  4. Item
    1. Title
    2. Date
    3. URL (of the item, sometimes called permalink)
    4. Description (body of the item)

The RSS feed for this will look something like:

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0"
xmlns:content="http://purl.org/rss/1.0/modules/content/"
xmlns:wfw="http://wellformedweb.org/CommentAPI/">

<channel>
<title>RSS Title</title>
<link>URL of Website</link>
<description><![CDATA[Description]]></description>
<language>en-us</language>
<pubDate>Sat, 07 Mar 2009 06:55:15 +0530</pubDate>

<item>
<title>Item Title</title>
<link>Item URL (Permalink)</link>
<pubDate>Sat, 07 Mar 2009 06:55:15 +0530</pubDate>
<description><![CDATA[Item Description]]></description>
</item>
</channel>
</rss>

Using FeddWriter abstracts working with and generating XML tags manually, you just tell FeedWriter what kind of Feed (RSS/Atom and version) you want; give it the data you want your feed to have and you’re done! The following code snippet shows you how exactly:

<?php
// Include the class
include("FeedWriter.php");

// Creating an instance of FeedWriter class.
// The parameter tell what type of
// feed you want.
$MyFeed = new FeedWriter(RSS2);

// Setting feed elements
$MyFeed->setTitle('My RSS Feed');
$MyFeed->setLink('http://www.example.com');
$MyFeed->setDescription('Test feed generated by Universal FeedWriter.');
$MyFeed->setChannelElement('pubDate'date(DATE_RSStime()));

// Create a FeedItem.
$Item $MyFeed->createNewItem();

// Add elements to the feed item.
$Item->setTitle('Item Title');
$Item->setLink('http://www.example.com/item1.html');
$Item->setDate(mktime(10,20,0,3,6,2008));
$Item->setDescription('Item Description. Can contain <b>HTML</b>.');

// Now add the item to the feed.
$MyFeed->addItem($Item);

// Now genarate the feed.
$MyFeed->genarateFeed();
?>

So you see how easy it is to generate a feed with the data we had.

Feeds generally don’t just have one item so let’s see something more real. The following code will generate a feed having ten items:

<?php
include("FeedWriter.php");

$MyFeed = new FeedWriter(RSS2);

$MyFeed->setTitle('My RSS Feed');
$MyFeed->setLink('http://www.example.com');
$MyFeed->setDescription('Test feed having Ten Items.');

$time mktime(10100352009);
$MyFeed->setChannelElement('pubDate'date(DATE_RSS$time));

for(
$i=0$i<10$i++)
{
    
$Item $MyFeed->createNewItem();

    
$Item->setTitle('Item' . ($i 1) . ' Title');
    
$Item->setLink('http://www.example.com/item' . ($i 1) . '.html');
    
// Have different dates for each item
    // Each will have one day gap for the
    // publishing time
    
$Item->setDate($time - ($i * (24 * (60 60))));
    
$Item->setDescription('Item ' . ($i+1) . ' Description.');

    
$MyFeed->addItem($Item);
}

$MyFeed->genarateFeed();
?>

One thing to note here is why we are using the feed’s generation time to be same as  that of the latest item rather than the current time when it is generated well, it’s because the feed gets updated only as and when new items are added (remains same at other time) and at the very same time. Therefore just because the feed is being generated dynamically at each request doesn’t mean it is “generate” at that time.

3 comments:

  1. great article..
    whether the way that was written above can be used for web-based joomla

    ReplyDelete
  2. greetings to all.
    I would first like to thank the writers of this blog by sharing information, a few years ago I read a book called guanacaste costa rica in this book deal with questions like this one.

    ReplyDelete
  3. FeedWriter is great but there's so many misspellings in the function names... :(

    ReplyDelete

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