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step6.md

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Step 6. Creating newsline RSS-feed

RSS — is an essential feature of any frequently updated web project. At this page we will show you how to create RSS feeds with Limb3.

Let's suppose we need to create RSS-feed with the latest news. To do so we'll create last-news-feed.php script and will put it into crud/www folder of our project.

The algorithm of last-news-feed.php is the following:

  • get the latest news
  • make absolute hrefs for news pages
  • push news record set to WACT template and convert it into XML
  • return RSS XML to client.

The source code of last-news-feed.php:

<?php
require_once('../setup.php');
require_once('limb/web_app/src/template/lmbWactTemplate.class.php');
require_once('limb/core/src/lmbCollection.class.php');
require_once('src/model/News.class.php');

$template = new lmbWactTemplate('rss/last_news.rss');
$template->setChildDataSet('last_news', getNewsDataSetWithFullPaths());

header("Content-Type: application/xml");

$template->display();

function getNewsDataSetWithFullPaths()
{
  $news_rs = lmbActiveRecord :: find('News', array('sort' => array('date' => 'DESC', 'title' => 'ASC'),
                                                   'limit' => 5));
  $result = array();
  foreach($news_rs as $news)
  {
    $news_id = $news->getId();
    $result[$news_id] = $news->export();
    $result[$news_id]['path'] = 'http://' . $_SERVER['HTTP_HOST'] . '/news/detail/' . $news_id;
  }

  return new lmbCollection($result);
}
?>

Let's explain what happens in the script above. The most interesting part is getNewsDataSetWithFullPaths() function where news are loaded from database using lmbActiveRecord :: find() method. News record set is sorted by «date» and «title» and limited with 5 elements. lmbActiveRecord :: find() method accepts class name of objects to be loaded and an array of parameters to be applied to the retrieved record set.

By the way, lmbActiveRecord :: find(..) part can be rewritten in a slightly different way using methods chaining:

$news_rs = lmbActiveRecord :: find('News')->sort(array('date' => 'DESC', 'title' => 'ASC'))->paginate(0, 5);

Once news are loaded we need to create a collection that contains news data as well as absolute paths to every news page:

$result = array();
foreach($news_rs as $news)
{
  $news_id = $news->getId();
  $result[$news_id] = $news->export();
  $result[$news_id]['path'] = 'http://' . $_SERVER['HTTP_HOST'] . '/news/detail/' . $news_id;
}
return new lmbCollection($result);

lmbCollection class is used above to create an iterator to be passed into WACT view.

Then WACT instance is created using rss/last_news.rss template followed by news collection passed into «last_news» runtime component of <list:list> tag:

$template = new lmbWactTemplate('rss/last_news.rss');
$template->setChildDataSet('last_news', getNewsDataSetWithFullPaths());

Here is rss/last_news.rss template contents:

<!--l version="1.0" encoding="utf-8"-->
<!DOCTYPE rss [<!ENTITY % HTMLlat1 PUBLIC "-//W3C//ENTITIES Latin 1 for XHTML//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml-lat1.ent">]>
<rss version="0.92" xml:base="http://tutorial.dbrain.bit">

<channel>
 <title>YourDomain.com last news</title>
 <language>en</language>

<list:list id='last_news'>
 <list:item>
  <item>
   <title>{$title}</title>
   <link>{$path}</link>
   <description>
      {$annotation}
   </description>
   <pubDate>
      {$date}
   </pubDate>
 </item>
  </list:item>
</list:list>
</channel>
</rss>

Please note how proper mime type is sent to the client:

header("Content-Type: application/xml");

Finally let's add a link to this RSS-feed into crud/template/page.html template:

<html>
<head>
  <title>Limb3 tutorial</title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body bgcolor="#FFFFFF" text="#000000" >
  <a href="/last-news-feed.php">RSS-feed</a>
  <hr />
  <core:PLACEHOLDER id="page_placeholder"/>
</body>
</html>

What's next?

Step 7. Further readings