Reading RSS with PHP

The Problem
The Internet seems to be getting easier everyday. With sites like Myspace, Flickr, YouTube, and Twitter, you can essentially create a full-on interactive web experience for free and with no knowledge of web design. This is great, but it limits your creativity, and it also requires your readers to remember multiple separate URLs.

On the flipside, you could reverse engineer all of these tools and create your own versions of them for use on your personal website, creating the same immersive user experience you get from using social tools, but that's a good deal of time and effort. The learning experience of building such tools is great, but we don't always have hundreds of hours to dedicate to rebuilding Flickr's robust photo management. Besides, doesn't it seem a little silly to reinvent the wheel?

So, what we're hoping for is a way to get the best of both worlds: how can we utilize the power of Flickr on our own website without needing to dedicate a great deal of time to solving the problem?

The Solution
One solution is to use RSS feeds to grab the content off of our various social media sites (in this example, we'll use Flickr). This way, we don't have to create any content at all. We simply need to grab the content from our account, figure out how to read it right into our website, and then display it in such a way that it will mesh with the rest of our site's design.

In this tutorial, we'll build a PHP class to load and parse a Flickr RSS feed, isolate the pieces of information we need, and output formatted XHTML to the browser. When we're done, it should look like this demo Flickr module.

Necessary Tools and Skills
I'm assuming for the purposes of this tutorial that you have a Flickr account, a basic understanding of PHP 5, and a good grasp on XHTML and CSS. You'll also need a server that supports PHP 5.

Collect the Pieces
Our first step is to find the RSS feed for our Flickr page. The feed is located at the bottom of the main photostream, and it looks like this:



You'll more than likely want to use the "Latest" option. After you click it, you'll get your browsers default RSS feed display, probably offering options to subscribe using a number of services. This is not what we're worried about, though. We want the URL of this page, which should look something like this:

http://api.flickr.com/services/feeds/photos_public.gne?id=22352410@N07&lang=en-us&format=rss_200

In a moment we'll use this URL to load our Flickr page into our website. But first, we need to tell our site how to handle this information.

Creating the Class
We start by creating a file named flickr.php and declaring the class flickr to contain all of our code:

<?php
  class flickr {

  }
?>

Now that we have our class, we need to declare all of the variables we're going to need. Because this is a pretty simple class, we only need one:

  var $feed;

The variable $feed will hold the URL of the Flickr page we're loading.

Next, we'll create a constructor for the class. This is the function that runs when the class is first instantiated. We'll use that to assign the feed URL to the class instance to allow our code to load the proper feed.

  function flickr($feed) {
    $this->feed = $feed;
  }

Now we have a class that has the address of our Flickr feed. Pretty simple so far, right?

Getting Our Information from the Feed
Here's where it starts getting a little tricky. Now we need to load that URL and parse it to extract the relevant information. To do this, we'll create a new function, parse:

  function parse() {
    $rss = simplexml_load_file($this->feed);
    $photodisp = array();
    foreach ($rss->channel->item as $item) {
      $link   = (string) $item->link; // Link to this photo
      $title = (string) $item->title; // Title of this photo
      $media  = $item->children('http://search.yahoo.com/mrss/');
      $thumb  = $media->thumbnail->attributes();
      $url    = (string) $thumb['url']; // URL of the thumbnail
      $width  = (string) $thumb['width']; // Width of the thumbnail
      $height = (string) $thumb['height']; // Height of the thumbnail

      $photodisp[] = <<<________________EOD

          <div class="flickr_photo">
            <a href="{$link}">
              <img src="{$url}"
                width="{$width}"
                height="{$height}"
                title="{$title}"
                alt="{$title}"
                style="border:0;" />
            </a>
          </div>
________________EOD;
    }

    return $photodisp;
  }

In order to pull down the information from this feed, we'll take advantage of the SimpleXML extension that was introduced in the release of PHP 5. To read more in-depth about this useful tool, there is a great article about SimpleXML on the Zend network.

In line 02, we load the feed from Flickr using the SimpleXML extension and place it in the variable $rss. This allows us to then extract data from the feed.

Line 03 creates the variable $photodisp, which is an array to hold each photo as we pull it out of the database.

In line 04, we start a foreach loop to break the feed into individual photos for processing.

Lines 05-11 load pieces of information from the feed into variable for use as we see fit. For the purposes of this class, we grab the URL for the photo's display page, the name of the photo, the location of the thumbnail image, and the thumbnail's width and height.

(Note: lines 07 and 08 load variables that we don't use for display; this is because the Flickr feed uses XML namespaces. These are a useful, albeit confusing, XML convention that helps prevent ambiguity of separate elements for easier reading. Our code is accessing the namespace contained in http://search.yahoo.com/mrss/ and identifying the thumbnail's URL, width, and height.)

Finally, in lines 14-26, we use the heredoc syntax to produce a formatted string of HTML that not only works well with CSS, but also looks great as source code (one of my pet peeves is hard-to-read source HTML)!

Each photo is stored in the array $photodisp for use in our next step: formatting for output.

Format Your Photos for Output
Now that we have all of the photos stored in an array, we set up a new function to create a web-ready block of HTML for displaying all of your photos.

  function display($numrows=6,$head="Photos on Flickr") {
    $photodisp = $this->parse();
    $i = 0;
    $thumbs = <<<____________EOD

      <!--// FlickrFeedr by Ennui Design
             www.EnnuiDesign.com | answers@ennuidesign.com //-->
        <div class="ennui_widget_head">
          {$head}
        </div>
        <div class="ennui_widget">
____________EOD;
    while ( $i < $numrows ) {
      $thumbs .= $photodisp[$i];
      $i++;
    }
    $trim = str_replace('http://api.flickr.com/services/feeds/photos_public.gne?id=', '',$this->feed);
    $user = str_replace('&lang=en-us&format=rss_200','',$trim);
    $thumbs .= <<<____________EOD

          <div class="ennui_widget_footer">
            <span>
              <a href="http://www.flickr.com/photos/{$user}/"
                title="http://www.flickr.com/photos/{$user}/">
                View All Photos on Flickr
              </a>
            </span>
          </div>
        </div>
      <!--// End FlickrFeedr by Ennui Design //-->
____________EOD;
    return $thumbs;
  }

Let's break that down. First, we'll be passing the variable $numrows when we call this function. This is how many photos we're going to display on the site. The default value is 6, which works well in 1, 2, and 3 column displays, making it a safe bet.

Then in line 02, we run the parse function we just created. This loads the array into the variable we'll call $photodisp for ease of use. Line 03 sets the variable $i to zero. We'll use this for a while loop to build our content.

Lines 04-10 start our output (using the heredoc syntax again). We're building the header of our display, as well as starting the div that will contain the photos.

The meat of this function happens in lines 11-14. Here, we are essentially telling the function, "while the number of photos we've grabbed is less than the number we're allowed to display, grab the next photo from the array." And, since we already formatted the output in the parse function, we don't have to do anything else with it!

In lines 17 and 18, we take the feed URL and trim out just the user name (in my Flickr feed, this user name is "22352410@N07"). This way, we can use it to send a site visitor to your Flickr photostream's homepage, eliminating any further data input or reliance on a visitor's memory of an additional URL.

Lines 19-27 finish up the HTML for the display, and then line 29 returns our output.

That's it! Now all we have to do is call the class and let 'er rip!

Implementing the Class
Our last step is to place the code on our homepage that will call this class and produce our new Flickr display!

<?php
  include('_class/flickr.php');
  $flickr = new flickr('http://api.flickr.com/services/feeds/photos_public.gne?id=22352410@N07&lang=en-us&format=rss_200');
  echo $flickr->display(8,"Ennui on Flickr");
?>

Wrap-Up
We have now successfully created a PHP class that loads, parses, and displays a Flickr user's photostream feed! With a little CSS styling and proper placement, you can now seamlessly integrate your Flickr stream into your own website.

Below, you can download the complete files used to create the fully functional Flickr RSS parsing demo.

Download the files for this tutorial (ZIP Archive, 2KB)

Enjoy! Please leave any questions and suggestions in the comments, as well as links to your site with the Flickr RSS parser in place!

Tags: flickr, rss, php, tutorial, simplexml