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PHP: Atom Feed Reader: Source Code

Based on the RSS Feed Reader, this is a similar class designed to parse Atom feeds and display them on a webpage as HTML. It's not been tested on all versions of the Atom format, but should be easy enough to customise.

Embedding an Atom Feed as HTML

Again, it's a simple class with a constructor and two public functions: getOutput returns an HTML-formatted version of the Atom feed, while getRawOutput returns all the attributes in a single multi-level array.

<?PHP
  include "class.myatomparser.php";

  # where is the feed located?
  $url = "http://www.example.net/atom.xml";

  # create object to hold data and display output
  $atom_parser = new myAtomParser($url);

  $output = $atom_parser->getOutput();	# returns string containing HTML
  echo $output;
?>

You can limit the number of entries displayed by passing an integer as the first argument to getOutput(), and if the encoding of your webpage doesn't match that of the feed you're subscribing to then you can pass the desired encoding as a second argument to getOutput() (e.g. ISO-8859-1). Otherwise by default the output of this class will use UTF-8 (Unicode).

Note: In some cases, for your request to get through, you will need to set a User Agent before calling the parser script.

Source code of class.myatomparser.php

This class is by no means the be-all and end-all of Atom parsing. It's designed to be simple, functional and easily customisable. Any feedback would be welcome.

File: class.myatomparser.php

<?PHP
  // Original PHP code by Chirp Internet: www.chirp.com.au
  // Please acknowledge use of this code by including this header.

  class myAtomParser
  {
    // keeps track of current and preceding elements
    var $tags = array();

    // array containing all feed data
    var $output = array();

    // return value for display functions
    var $retval = "";

    var $encoding = array();

    // constructor for new object
    function myAtomParser($file)
    {
      // instantiate xml-parser and assign event handlers
      $xml_parser = xml_parser_create("");
      xml_set_object($xml_parser, $this);
      xml_set_element_handler($xml_parser, "startElement", "endElement");
      xml_set_character_data_handler($xml_parser, "parseData");

      // open file for reading and send data to xml-parser
      $fp = @fopen($file, "r") or die("<b>myAtomParser Error:</b> Could not open URL $file for input");
      while($data = fread($fp, 4096)) {
        xml_parse($xml_parser, $data, feof($fp)) or die(
          sprintf("myAtomParser: Error <b>%s</b> at line <b>%d</b><br>",
          xml_error_string(xml_get_error_code($xml_parser)),
          xml_get_current_line_number($xml_parser))
        );
      }
      fclose($fp);

      // dismiss xml parser
      xml_parser_free($xml_parser);
    }

    function startElement($parser, $tagname, $attrs)
    {
      if($this->encoding) {
        // content is encoded - so keep elements intact
        $tmpdata = "<$tagname";
        if($attrs) foreach($attrs as $key => $val) $tmpdata .= " $key=\"$val\"";
        $tmpdata .= ">";
        $this->parseData($parser, $tmpdata);
      } else {
        if($attrs['HREF'] && $attrs['REL'] && $attrs['REL'] == 'alternate') {
          $this->startElement($parser, 'LINK', array());
          $this->parseData($parser, $attrs['HREF']);
          $this->endElement($parser, 'LINK');
        }
        if($attrs['TYPE']) $this->encoding[$tagname] = $attrs['TYPE'];

        // check if this element can contain others - list may be edited
        if(preg_match("/^(FEED|ENTRY)$/", $tagname)) {
          if($this->tags) {
            $depth = count($this->tags);
            list($parent, $num) = each($tmp = end($this->tags));
            if($parent) $this->tags[$depth-1][$parent][$tagname]++;
          }
          array_push($this->tags, array($tagname => array()));
        } else {
          // add tag to tags array
          array_push($this->tags, $tagname);
        }
      }
    }

    function endElement($parser, $tagname)
    {
      // remove tag from tags array
      if($this->encoding) {
        if(isset($this->encoding[$tagname])) {
          unset($this->encoding[$tagname]);
          array_pop($this->tags);
        } else {
          if(!preg_match("/(BR|IMG)/", $tagname)) $this->parseData($parser, "</$tagname>");
        }
      } else {
        array_pop($this->tags);
      }
    }

    function parseData($parser, $data)
    {
      // return if data contains no text
      if(!trim($data)) return;
      $evalcode = "\$this->output";
      foreach($this->tags as $tag) {
        if(is_array($tag)) {
          list($tagname, $indexes) = each($tag);
          $evalcode .= "[\"$tagname\"]";
          if(${$tagname}) $evalcode .= "[" . (${$tagname} - 1) . "]";
          if($indexes) extract($indexes);
        } else {
          if(preg_match("/^([A-Z]+):([A-Z]+)$/", $tag, $matches)) {
            $evalcode .= "[\"$matches[1]\"][\"$matches[2]\"]";
          } else {
            $evalcode .= "[\"$tag\"]";
          }
        }
      }

      if(isset($this->encoding['CONTENT']) && $this->encoding['CONTENT'] == "text/plain") {
        $data = "<pre>$data</pre>";
      }

      eval("$evalcode .= '" . addslashes($data) . "';");
    }

    // display a single feed as HTML
    function display_feed($data, $limit)
    {
      extract($data);
      if($TITLE) {
        // display feed information
        $this->retval .= "<h1>";
        if($LINK) $this->retval .= "<a href=\"$LINK\" target=\"_blank\">";
        $this->retval .= stripslashes($TITLE);
        if($LINK) $this->retval .= "</a>";
        $this->retval .= "</h1>\n";
        if($TAGLINE) $this->retval .= "<P>" . stripslashes($TAGLINE) . "</P>\n\n";
        $this->retval .= "<div class=\"divider\"><!-- --></div>\n\n";
      }
      if($ENTRY) {
        // display feed entry(s)
        foreach($ENTRY as $item) {
          $this->display_entry($item, "FEED");
          if(is_int($limit) && --$limit <= 0) break;
        }
      }
    }

    // display a single entry as HTML
    function display_entry($data, $parent)
    {
      extract($data);
      if(!$TITLE) return;

      $this->retval .=  "<p><b>";
      if($LINK) $this->retval .=  "<a href=\"$LINK\" target=\"_blank\">";
      $this->retval .= stripslashes($TITLE);
      if($LINK) $this->retval .= "</a>";
      $this->retval .=  "</b>";
      if($ISSUED) $this->retval .= " <small>($ISSUED)</small>";
      $this->retval .=  "</p>\n";

      if($AUTHOR) {
        $this->retval .=  "<P><b>Author:</b> " . stripslashes($AUTHOR['NAME']) . "</P>\n\n";
      }
      if($CONTENT) {
        $this->retval .=  "<P>" . stripslashes($CONTENT) . "</P>\n\n";
      } elseif($SUMMARY) {
        $this->retval .=  "<P>" . stripslashes($SUMMARY) . "</P>\n\n";
      }
    }

    function fixEncoding($input, $output_encoding)
    {
      if(!function_exists('mb_detect_encoding')) return $input;

      $encoding = mb_detect_encoding($input);
      switch($encoding)
      {
        case 'ASCII':
        case $output_encoding:
          return $input;
        case '':
          return mb_convert_encoding($input, $output_encoding);
        default:
          return mb_convert_encoding($input, $output_encoding, $encoding);
      }
    }

    // display entire feed as HTML
    function getOutput($limit=false, $output_encoding='UTF-8')
    {
      $this->retval = "";
      $start_tag = key($this->output);

      switch($start_tag)
      {
        case "FEED":
          foreach($this->output as $feed) $this->display_feed($feed, $limit);
          break;
        default:
          die("Error: unrecognized start tag '$start_tag' in getOutput()");
      }

      return $this->fixEncoding($this->retval, $output_encoding);
    }

    // return raw data as array
    function getRawOutput($output_encoding='UTF-8')
    {
      return $this->fixEncoding($this->output, $output_encoding);
    }
  }
?>

expand code box

Here you can copy the code for class.myatomparser.php:

<?PHP
 // Original PHP code by Chirp Internet: www.chirp.com.au
 // Please acknowledge use of this code by including this header.

class myAtomParser
  {
    // keeps track of current and preceding elements
    var $tags = array();

// array containing all feed data
    var $output = array();

// return value for display functions
    var $retval = "";

var $encoding = array();

// constructor for new object
    function myAtomParser($file)
    {
      // instantiate xml-parser and assign event handlers
      $xml_parser = xml_parser_create("");
      xml_set_object($xml_parser, $this);
      xml_set_element_handler($xml_parser, "startElement", "endElement");
      xml_set_character_data_handler($xml_parser, "parseData");

// open file for reading and send data to xml-parser
 $fp = @fopen($file, "r") or die("myAtomParser Error: Could not open URL $file for input");
 while($data = fread($fp, 4096)) {
 xml_parse($xml_parser, $data, feof($fp)) or die(
 sprintf("myAtomParser: Error %s at line %d ",
 xml_error_string(xml_get_error_code($xml_parser)),
 xml_get_current_line_number($xml_parser))
 );
 }
 fclose($fp);

// dismiss xml parser
      xml_parser_free($xml_parser);
    }

function startElement($parser, $tagname, $attrs)
 {
 if($this->encoding) {
 // content is encoded - so keep elements intact
 $tmpdata = "<$tagname";
 if($attrs) foreach($attrs as $key => $val) $tmpdata .= " $key=\"$val\"";
 $tmpdata .= ">";
 $this->parseData($parser, $tmpdata);
 } else {
 if($attrs['HREF'] && $attrs['REL'] && $attrs['REL'] == 'alternate') {
 $this->startElement($parser, 'LINK', array());
 $this->parseData($parser, $attrs['HREF']);
 $this->endElement($parser, 'LINK');
 }
 if($attrs['TYPE']) $this->encoding[$tagname] = $attrs['TYPE'];

// check if this element can contain others - list may be edited
        if(preg_match("/^(FEED|ENTRY)$/", $tagname)) {
          if($this->tags) {
            $depth = count($this->tags);
            list($parent, $num) = each($tmp = end($this->tags));
            if($parent) $this->tags[$depth-1][$parent][$tagname]++;
          }
          array_push($this->tags, array($tagname => array()));
        } else {
          // add tag to tags array
          array_push($this->tags, $tagname);
        }
      }
    }

if(isset($this->encoding['CONTENT']) && $this->encoding['CONTENT'] == "text/plain") {
 $data = "<pre>$data</pre>";
 }

eval("$evalcode .= '" . addslashes($data) . "';");
    }

// display a single feed as HTML
 function display_feed($data, $limit)
 {
 extract($data);
 if($TITLE) {
 // display feed information
 $this->retval .= "<h1>";
 if($LINK) $this->retval .= "<a href=\"$LINK\" target=\"_blank\">";
 $this->retval .= stripslashes($TITLE);
 if($LINK) $this->retval .= "</a>";
 $this->retval .= "</h1>\n";
 if($TAGLINE) $this->retval .= "" . stripslashes($TAGLINE) . "\n\n";
 $this->retval .= "<div class=\"divider\"></div>\n\n";
 }
 if($ENTRY) {
 // display feed entry(s)
 foreach($ENTRY as $item) {
 $this->display_entry($item, "FEED");
 if(is_int($limit) && --$limit <= 0) break;
 }
 }
 }

// display a single entry as HTML
    function display_entry($data, $parent)
    {
      extract($data);
      if(!$TITLE) return;

$this->retval .= "";
 if($LINK) $this->retval .= "<a href=\"$LINK\" target=\"_blank\">";
 $this->retval .= stripslashes($TITLE);
 if($LINK) $this->retval .= "</a>";
 $this->retval .= "";
 if($ISSUED) $this->retval .= " ($ISSUED)";
 $this->retval .= "\n";

if($AUTHOR) {
 $this->retval .= "Author: " . stripslashes($AUTHOR['NAME']) . "\n\n";
 }
 if($CONTENT) {
 $this->retval .= "" . stripslashes($CONTENT) . "\n\n";
 } elseif($SUMMARY) {
 $this->retval .= "" . stripslashes($SUMMARY) . "\n\n";
 }
 }

function fixEncoding($input, $output_encoding)
    {
      if(!function_exists('mb_detect_encoding')) return $input;

$encoding = mb_detect_encoding($input);
      switch($encoding)
      {
        case 'ASCII':
        case $output_encoding:
          return $input;
        case '':
          return mb_convert_encoding($input, $output_encoding);
        default:
          return mb_convert_encoding($input, $output_encoding, $encoding);
      }
    }

// display entire feed as HTML
    function getOutput($limit=false, $output_encoding='UTF-8')
    {
      $this->retval = "";
      $start_tag = key($this->output);

switch($start_tag)
      {
        case "FEED":
          foreach($this->output as $feed) $this->display_feed($feed, $limit);
          break;
        default:
          die("Error: unrecognized start tag '$start_tag' in getOutput()");
      }

return $this->fixEncoding($this->retval, $output_encoding);
    }

// return raw data as array
    function getRawOutput($output_encoding='UTF-8')
    {
      return $this->fixEncoding($this->output, $output_encoding);
    }
  }
?>

Fields Supported by Default

This script supports the following attributes (fields) by default but can easily be extended. See the Feed Reader Demonstration for examples of parsed Atom (and RSS) feeds.

Channel (FEED)

Title
Link (HREF, Rel)
Tagline

Item (ENTRY)

Title (required)
Link (HREF, Rel)
Issued
Author (Name)
Content or Summary

If you think it's worth adding support for other Atom attributes, please let us know using the Feedback link below.

PHP: RSS and Atom Feed Reader
PHP: RSS Feed Reader: Source Code
PHP: RSS Feed Reader Code Example
PHP: Atom Feed Reader: Source Code
PHP: YouTube API Feed Reader: Source Code
PHP: Displaying and updating RSS Content using Ajax
PHP: Displaying Twitter Search Results in HTML

User Comments and Notes

Botond Zalai 21 September, 2007

This script is great, but in order to use a blogger atom feed in my page I had to do an encoding conversion.

Thanks for your feedback Botond. You can see that I've now added some code to handle character encoding differences between the feed source and the page where it's displayed.

trevor 9 October, 2007

This code totally rocks!

I was banging my head against the wall for 3 days until i found your solution for blogspot atom feeds. I called the xml from my php server and granted access to the flash movie on the third server and from that server called the php file which basically echos the blogspot feed.

That sounds a bit complicated to me, but as long as it works

Hank 20 December, 2007

Is there a way to limit the output to say 5 or 6 entries? I am not very good at PHP but I know there has got to be a way to do it...

Just replace "getOutput()" with "getOutput(5)" in the example code to limit the output to the first 5 entries.

Ken 6 January, 2008

You say the function getRawOutput() returns an array. What are the keys in the array?

The best way to find that out would be to use the print_r function to display all the contents of the array. There's also an example on this page.

Pascal 25 June, 2008

I've tested this PHP class and therefor I'd like to use it in other PHP projects. Therefor I have to know under which license this PHP class is published. Can you please add this information? Thanks!

Hi Pascal, this class is available under an open source licence.

Kevin Creighton 17 July, 2008

One quick question: Is it possible for me to remove the "Author" field from the output, and if so, how is that accomplished?

Again, let me congratulate on this simple, elegant solution that works for for even PHP dummies like me.

Just remove the code block from display_entry() that starts with if($AUTHOR) as that's where the Author is displayed.

Evan Robinson 18 September, 2008

I couldn't have added the twitter feed nearly as easily without this code. I'm afraid that I butchered the output unmercifully in order to get it into mySQL instead of on the page, but the underlying code worked great and was easy to understand and modify. Thanks for a great resource!

dave 28 February, 2009

i am happy to have found this. question though. not sure what i am doing wrong. i get back tons of these:

Notice: Undefined index: HREF in ...
Notice: Undefined index: TYPE in ...

can't figure it out

Are you sure your feed contains valid XML? It looks like you it might have some HTML that is not properly encoded. You should try validating your feed as a first step.

G 6 July, 2009

Is there a way to show the publish date of the post? And if possible, the time.

The feed parser extracts all fields from the feed into an array. You can then modify the display_entry function to display them how you want. Or use the raw data as shown in some of the related articles above.

Michael Blow 16 December, 2009

Using your atom feed reader and I have the same problem as Dave (28/02/2009): a whole list of 'undefined index' statements. I've validated the feed and comes back as valid atom 1.0 - its just a feed from blogspot. Also I have used your class in the past and it worked fine.

Those are just notices/warnings and not actual errors. You can hide them by changing your error_reporting level in PHP. See the comments here. The way the parseData function is written with the eval() statement makes it almost impossible to avoid referencing undefined variables.

Anthony Clough 9 January, 2010

Great resource. I am just beginning to use php and found this very usefull in parsing xml feeds from a variety of sources! Thanks for posting your work!

Josh 1 September, 2010

I am getting an error : "myAtomParser Error: Could not open URL" when I upload to a production server. This works fine locally for testing, any thoughts?

Try removing the '@' from in front of the fopen() command so you can see what the actual error is:

# open file for reading and send data to xml-parser $fp = @fopen($file, "r") or die("myAtomParser Error: Could not open URL $file for input")

Mostly likely your request is being blocked/denied by the target server based on your IP address or user agent. Or the URL/path is invalid.

avantegrate 13 January, 2011

Please explain how to get time field
like "6 hours ago" using the class

First use strtotime to convert the time string into a timestamp, then pass that to the function here.

gw2297 28 January, 2011

Getting the following error:
Fatal error: Cannot use assign-op operators with overloaded objects nor string offsets in ~/public_html/class.myatomparser.php: eval()'d code on line 1
Any suggestions?
Thanks in advance!

Sorry, not something I've seen. Perhaps you can try echoing the command being eval'd to see what's actually being executed and causing problems?

Emery Wooten 29 January, 2011

Thanks for the atom feed reader code. Since the National Weather Service switched from RSS to Atom I needed an atom reader and found yours on Google. It worked right out of the box!

I modified the code to use CSS instead of inserting the html tags. I also modified it to use cURL instead of fopen and also to create cache files.

Thanks again!

Emery Wooten 29 January, 2011

The reader is not detecting links. Try it with this atom 1.0 feed.

www.weather.gov/alerts-beta/wwaatmget.php?x=ALZ064

The Atom parser class looks for LINK elements with both an 'HREF' attribute and 'REL="alternate"'.
if($attrs['HREF'] && $attrs['REL'] && $attrs['REL'] == 'alternate') {
The feed you're using is missing the 'REL' attribute so you need to change that line to just:
if($attrs['HREF']) {
Some other Atom feeds have multiple LINK tags and normally looking for 'rel="alternate"' tells us which one to use when displaying the feed.

Ed 15 March, 2011

Excellent! Looked for a couple of days for a php script that does exactly this.

I want this to show just the last two feeds, is this done by changing this line

function getOutput($limit=false, $output_encoding='UTF-8'

to

function getOutput($limit=2, $output_encoding='UTF-8'

??

No, no, no. You change the function call from getOutput() to getOutput(2). Those are optional parameters for the function with default values. Read the instructions at the top of the page

Dionn Schaffner 14 April, 2011

I installed all the files, but I keep getting a "Could not open URL" error. I double checked and my php.ini for PHP5 file has the allow_url_fopen option enabled. What am I missing?

There are no problems accessing your feed from our server. If it's still not working you should check your server logs for errors - on the site running the script (for PHP warnings) and the one hosting the RSS feed (for Apache errors).

ABC 17 November, 2011

Is it possible to define a number of characters to display per entry? ie. i want to display the first 40 characters of each entry in the feed

You can add code to truncate the text for each feed entry. It would need to be added to the display_entry function.