Code-Tips.com - Web Development, Programming, SEO

In this tutorial, I demonstrate how to generate a feed using Php that can be displayed from a website in multiple formats, including Atom 1.0 and RSS 2.0.  I will be using functionality from the Php FeedWriter class library to generate the feed, which is available for free at http://phpFeedWriter.webmasterhub.net/.

Summary

• Prepare your feed script/page - Instantiate a (Php) FeedWriter Class Object
• Add additional (Channel) data to the feed
• Add Items to the Feed
• Get the specified feed output format
• (Optional) Set the “Content” element of each feed item as type “HTML”
• Output the Feed XML
• (Optional) Writing to a file / Caching Feed Content

Prepare your feed script/page - Instantiate a (Php) FeedWriter Class Object

1. Download the latest version of the Php feedWriter Class library (free)

2. Extract the package to a new directory on your web server that supports Php.  

3. Create a new file called "feed.php".  

4. Paste the following code into the file.

/* Example Feed using Php FeedWriter http://phpFeedWriter.webmasterhub.net/ 
 * Example feed: http://phpfeedwriter.webmasterhub.net/samples/1/feed.php
 *
 * View the tutorial: http://www.code-tips.com/2011/08/how-to-generate-feed-using-php-atom-10.html 
 */
require_once('feed/FeedWriter.php');

//Block 1 ----------------------------------------------
//Title if the feed
$feed_title = 'Example Feed using Php FeedWriter';

//Feed Link.  This should be a URL to the website, or blog that content displayed in the feed is from.
$feed_link = 'http://www.code-tips.com/';

//A short description of the feed.
$feed_description = 'This is an exmaple feed created as part of the tutorial on code-tips.com for generating RSS / Atom feeds using Php.';

//Instantiate the FeedWriter class
$feedWriter = new FeedWriter(
	$feed_title, 	//Feed Title
	$feed_description, //Feed Description
	$feed_link, //Feed Link
	6, //indent
	true, //Use CDATA
	null, //encoding
	true //enable validation
	);

//Enable debug
$feedWriter->debug = true;

5. In the code you have just pasted, replace the example title, description and feed link with your own.

• When developing the feed, you should enable validation to ensure that you have included enough information in the feed for it to be valid in each output format.  
• The option to enable CDATA will result in character data (CDATA) tags being written where text content is included in the feed.  This may be required depending on the type of information you are adding to the feed, and how you would like it to be displayed.  
• It is also possible to set the character encoding for the feed output when constructing the FeedWriter object.  In this example, I have set this to null so that it uses the default (EN-US).  
• Enabling validation ( $feedWriter->debug = true; ) will also assist when developing the feed, as additional information is provided when a feed is not valid instead of a generic message.  The information includes the specific elements  in the feed schema  used to output the feed that were missing required information.  Links are also provided to the relevant documentation on the Php FeedWriter website.

Add additional (Channel) data to the feed

6. Paste the lines of code in the following steps one after another, after the first code block included in the file.  Change the values as necessary.

• Set an image for the feed (Required for some RSS formats)

$feedWriter->set_image('WebmasterHub.net', 'http://www.webmasterhub.net/img/logo.jpg','http://www.webmasterhub.net/');

• Specify the language of the feed content (Required for some formats)

$feedWriter->set_language('EN-US');

• Specify the date that content in the feed was last updated (Required for Atom 1.0)

$feedWriter->set_date('2011-08-12T00:00:00Z',DATE_UPDATED);

• Include contact details of the feed author (Required for Atom 1.0)

$feedWriter->set_author(null, 'Daniel','http://www.code-tips.com/');

• Set the “Self Link”, which is the URL to the feed. (Required for Atom 1.0)

$feedWriter->set_selfLink('http://phpfeedwriter.webmasterhub.net/samples/1/feed.php');

Add Items to the Feed

7. Paste the following code block into the file, after the previous code

//Block 3 ----------------------------------------------
//Create/Retrieve array containing data for the sample items 
//this array should be replaced with your database query result array or similar

//## Section 3.1 - Items Array
$items = Array();
$items[] = Array( 
	//Example Item 1
	'item_title' => 'Php FeedWriter Example Feed: Item',
	'item_content' => 'This is an example item. 
 This HTML should be rendered when the feed is displayed in a browser or reader that supports HTML output...',
	'item_link' => 'http://www.code-tips.com/link_to_post.html',
	'item_published' => '2011-08-12T00:00:00Z',
	'item_updated' => '2011-08-12T00:00:00Z');
$items[] = Array( 
	//Example Item 2
	'item_title' => 'Php FeedWriter Example Feed: Item 2',
	'item_link' => 'http://phpfeedwriter.webmasterhub.net/',
	'item_published' => '2011-08-12T00:00:00Z',
	'item_updated' => '2011-08-12T00:00:00Z');


//## Section 3.2 - Loop through the items array, add items to the feed
foreach($items as $item)
{
	//Get the title, content, link for the current item if supplied.
	if(isset($item['item_title']))
		$item_title = $item['item_title'];
	else
		$item_title = null;
		
	if(isset($item['item_content']))
		$item_content = $item['item_content'];
	else
		$item_content = null;
		
	if(isset($item['item_link']))
		$item_link = $item['item_link'];
	else
		$item_link = null;
	
	//Add the current item to the feed
	$feedWriter->add_item($item_title, $item_content, $item_link);
	
	//Add additional data to the current item if available
	if(isset($item['item_updated']))
		$feedWriter->set_date($item['item_updated'], DATE_UPDATED);
		
	if(isset($item['item_published']))
		$feedWriter->set_date($item['item_published'], DATE_PUBLISHED);
}

8. Set the items array (section 1 of code block 3) to your data source, or leave the example array in place to continue and test the feed.
9. Update the Loop component (section 2 of code block 3) so that the array key values match your items array, or replace with your own values as required.

Get the specified feed output format

10. Paste the following code into your php file on an empty line after the code block added in the previous step.

//Block 4 ----------------------------------------------
//Get the format to display in, 
//set to RSS 2.0 as default or if format is not found
$format = Atom_1;
if(isset($_GET['format']) && $_GET['format'] != null)
{
	foreach($feedWriter->getFeedFormats() as $curFormat)
	{
		if($curFormat[0] == $_GET['format'])
			$format = $curFormat[1];
	}
}

(Optional) Set the “Content” element of each feed item as type “HTML”

11. Paste the following code into your Php file on an empty line after the code from the previous step.

//Block 5 ----------------------------------------------
//Set the item body/content output type to html for the selected output format
$feedWriter->set_feedConstruct($format);
$feedWriter->feed_construct->construct['itemContent']['type'] = 'html'; 

• For more information, and a full list of constructs for each format, see Predefined Feed Constructs.  
• For a list of the abstracted values such as “itemContent” used to represent similar elements across multiple formats, see commonName Values.  

Output the Feed XML

12. Copy the following code into the file after the block added in the previous step

//Block 6 ----------------------------------------------
//Build and output the feed XML in the specified, or default format
//--------------------------------
echo $feedWriter->getXML($format);  

(Optional) Writing to a file / caching feed content

$feedWriter->writeToFile('filename.xml',$format);