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RSS

The RSS helper makes generating XML for RSS feeds easy.

Creating an RSS feed with the RssHelper

This example assumes you have a Posts Controller and Post Model already created and want to make an alternative view for RSS.

Creating an xml/rss version of posts/index is a snap with CakePHP 1.3. After a few simple steps you can simply append the desired extension .rss to posts/index making your URL posts/index.rss. Before we jump too far ahead trying to get our webservice up and running we need to do a few things. First parseExtensions needs to be activated, this is done in app/config/routes.php

Router::parseExtensions('rss');

In the call above we’ve activated the .rss extension. When using Router::parseExtensions() you can pass as many arguments or extensions as you want. This will activate each extension/content-type for use in your application. Now when the address posts/index.rss is requested you will get an xml version of your posts/index. However, first we need to edit the controller to add in the rss-specific code.

Controller Code

It is a good idea to add RequestHandler to your PostsController’s $components array. This will allow a lot of automagic to occur.

var $components = array('RequestHandler');

Our view will also use the TextHelper for formatting, so that should be added to the controller as well.

var $helpers = array('Text');

Before we can make an RSS version of our posts/index we need to get a few things in order. It may be tempting to put the channel metadata in the controller action and pass it to your view using the Controller::set() method but this is inappropriate. That information can also go in the view. That will come later though, for now if you have a different set of logic for the data used to make the RSS feed and the data for the html view you can use the RequestHandler::isRss() method, otherwise your controller can stay the same.

// Modify the Posts Controller action that corresponds to
// the action which deliver the rss feed, which is the
// index action in our example

public function index(){
    if( $this->RequestHandler->isRss() ){
        $posts = $this->Post->find('all', array('limit' => 20, 'order' => 'Post.created DESC'));
        return $this->set(compact('posts'));
    }

    // this is not an Rss request, so deliver
    // data used by website's interface
    $this->paginate['Post'] = array('order' => 'Post.created DESC', 'limit' => 10);

    $posts = $this->paginate();
    $this->set(compact('posts'));
}

With all the View variables set we need to create an rss layout.

Layout

An Rss layout is very simple, put the following contents in app/views/layouts/rss/default.ctp:

echo $this->Rss->header();
if (!isset($documentData)) {
    $documentData = array();
}
if (!isset($channelData)) {
    $channelData = array();
}
if (!isset($channelData['title'])) {
    $channelData['title'] = $title_for_layout;
}
$channel = $this->Rss->channel(array(), $channelData, $content_for_layout);
echo $this->Rss->document($documentData,$channel);

It doesn’t look like much but thanks to the power in the RssHelper its doing a lot of lifting for us. We haven’t set $documentData or $channelData in the controller, however in CakePHP 1.3 your views can pass variables back to the layout. Which is where our $channelData array will come from setting all of the meta data for our feed.

Next up is view file for my posts/index. Much like the layout file we created, we need to create a views/posts/rss/ directory and create a new index.ctp inside that folder. The contents of the file are below.

View

Our view, located at app/views/posts/rss/index.ctp, begins by setting the $documentData and $channelData variables for the layout, these contain all the metadata for our RSS feed. This is done by using the View::set() method which is analogous to the Controller::set() method. Here though we are passing the channel’s metadata back to the layout.

$this->set('documentData', array(
    'xmlns:dc' => 'http://purl.org/dc/elements/1.1/'));

$this->set('channelData', array(
    'title' => __("Most Recent Posts", true),
    'link' => $this->Html->url('/', true),
    'description' => __("Most recent posts.", true),
    'language' => 'en-us'));

The second part of the view generates the elements for the actual records of the feed. This is accomplished by looping through the data that has been passed to the view ($items) and using the RssHelper::item() method. The other method you can use, RssHelper::items() which takes a callback and an array of items for the feed. (The method I have seen used for the callback has always been called transformRss(). There is one downfall to this method, which is that you cannot use any of the other helper classes to prepare your data inside the callback method because the scope inside the method does not include anything that is not passed inside, thus not giving access to the TimeHelper or any other helper that you may need. The RssHelper::item() transforms the associative array into an element for each key value pair.

You will need to modify the $postLink variable as appropriate to your application.

foreach ($posts as $post) {
    $postTime = strtotime($post['Post']['created']);

    $postLink = array(
        'controller' => 'posts',
        'action' => 'view',
        'year' => date('Y', $postTime),
        'month' => date('m', $postTime),
        'day' => date('d', $postTime),
        $post['Post']['slug']);
    // You should import Sanitize
    App::import('Sanitize');
    // This is the part where we clean the body text for output as the description
    // of the rss item, this needs to have only text to make sure the feed validates
    $bodyText = preg_replace('=\(.*?\)=is', '', $post['Post']['body']);
    $bodyText = $this->Text->stripLinks($bodyText);
    $bodyText = Sanitize::stripAll($bodyText);
    $bodyText = $this->Text->truncate($bodyText, 400, array(
        'ending' => '...',
        'exact'  => true,
        'html'   => true,
    ));

    echo  $this->Rss->item(array(), array(
        'title' => $post['Post']['title'],
        'link' => $postLink,
        'guid' => array('url' => $postLink, 'isPermaLink' => 'true'),
        'description' =>  $bodyText,
        'dc:creator' => $post['Post']['author'],
        'pubDate' => $post['Post']['created']));
}

You can see above that we can use the loop to prepare the data to be transformed into XML elements. It is important to filter out any non-plain text characters out of the description, especially if you are using a rich text editor for the body of your blog. In the code above we use the TextHelper::stripLinks() method and a few methods from the Sanitize class, but we recommend writing a comprehensive text cleaning helper to really scrub the text clean. Once we have set up the data for the feed, we can then use the RssHelper::item() method to create the XML in RSS format. Once you have all this setup, you can test your RSS feed by going to your site /posts/index.rss and you will see your new feed. It is always important that you validate your RSS feed before making it live. This can be done by visiting sites that validate the XML such as Feed Validator or the w3c site at http://validator.w3.org/feed/.

You may need to set the value of ‘debug’ in your core configuration to 1 or to 0 to get a valid feed, because of the various debug information added automagically under higher debug settings that break XML syntax or feed validation rules.