Question

the code below is tested and working, it prints the contents of a feed that has this structure.

<rss>
    <channel>
        <item>
            <pubDate/>
            <title/>
            <description/>
            <link/>
            <author/>
        </item>
    </channel>
</rss>

What I didn’t manage to succesfully do is to print feeds that follow this structure below (the difference is on <feed><entry><published> ) even though I changed the xpath to /feed//entry.
you can see the structure on the page source.

<feed>
    <entry>
        <published/>
        <title/>
        <description/>
        <link/>
        <author/>
    </entry>
</feed>

I have to say that the code sorts all item based on its pubDate. In the second structure feed I guess it should sort all entry based on its published.

I probably make a mistake on the xPath I can’t find. However, if at the end of this I manage to print that feed right, how can I modify the code to handle different structures all at once ?

Is there any service that allow me to create and host my own feeds based on those feeds, so I will have the same structure to all? I hope I made my self clear… Thank you.

<?php

$feeds = array();

// Get all feed entries
$entries = array();
foreach ($feeds as $feed) {
    $xml = simplexml_load_file($feed);
    $entries = array_merge($entries, $xml->xpath(''));
}

?>

Answer 1

The main contribution of this answer is a solution (at the end) that can be used with infinite number of formats, just specifying all “entry” alternative names in the external (global) parameter $postElements and all “published-date” alternative names in the external (global) parameter $pub-dateElements.

Besides this, here is how to specify an XPath expression that selects all /rss//item and all /feed//entry elements.

In the simple case of just two possible document formats this (as proposed by @Josh Davis) Xpath expression correctly works:

/rss//item  |   /feed//entry

A more general XPath expression allows the selection of the wanted elements from a set of unlimited number of document formats:

/*[contains($topElements, concat('|',name(),'|'))]
    //*[contains($postElements, concat('|',name(),'|'))]

where the variable $topElements should be substituted by a pipe-delimited string of all possible names for a top element, and $postElements should be substituted by a pipe-delimited string of all possible names for a “entry” element. We also allow the “entry” elements to be at different depths in the different document formats.

In particular, for this concrete case the XPath expression will be;

/*[contains('|feed|rss|', concat('|',name(),'|'))]
    //*[contains('|item|entry|', concat('|',name(),'|'))]

The rest of this post shows how the complete wanted processing can be done entirely in XSLT — easily and with elegance.

---

I. A gentle introduction

Such processing is easy and simple with XSLT:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="/">
  <myFeed>
   <xsl:apply-templates/>
  </myFeed>
 </xsl:template>

 <xsl:template match="channel|feed">
  <xsl:apply-templates select="*">
   <xsl:sort select="pubDate|published" order="descending"/>
  </xsl:apply-templates>
 </xsl:template>

 <xsl:template match="item|entry">
  <post>
    <xsl:apply-templates mode="identity"/>
  </post>
 </xsl:template>

 <xsl:template match="pubDate|published" mode="identity">
  <publicationDate>
   <xsl:apply-templates/>
  </publicationDate>
 </xsl:template>

  <xsl:template match="node()|@*" mode="identity">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*" mode="identity"/>
  </xsl:copy>
 </xsl:template>
</xsl:stylesheet>

when this transformation is applied to this XML document (in format 1):

<rss>
    <channel>
        <item>
            <pubDate>2011-06-05</pubDate>
            <title>Title1</title>
            <description>Description1</description>
            <link>Link1</link>
            <author>Author1</author>
        </item>
        <item>
            <pubDate>2011-06-06</pubDate>
            <title>Title2</title>
            <description>Description2</description>
            <link>Link2</link>
            <author>Author2</author>
        </item>
        <item>
            <pubDate>2011-06-07</pubDate>
            <title>Title3</title>
            <description>Description3</description>
            <link>Link3</link>
            <author>Author3</author>
        </item>
    </channel>
</rss>

and when it is applied on this equivalent document (in format 2):

<feed>
        <entry>
            <published>2011-06-05</published>
            <title>Title1</title>
            <description>Description1</description>
            <link>Link1</link>
            <author>Author1</author>
        </entry>
        <entry>
            <published>2011-06-06</published>
            <title>Title2</title>
            <description>Description2</description>
            <link>Link2</link>
            <author>Author2</author>
        </entry>
        <entry>
            <published>2011-06-07</published>
            <title>Title3</title>
            <description>Description3</description>
            <link>Link3</link>
            <author>Author3</author>
        </entry>
</feed>

in both cases the same wanted, correct result is produced:

<myFeed>
   <post>
      <publicationDate>2011-06-07</publicationDate>
      <title>Title3</title>
      <description>Description3</description>
      <link>Link3</link>
      <author>Author3</author>
   </post>
   <post>
      <publicationDate>2011-06-06</publicationDate>
      <title>Title2</title>
      <description>Description2</description>
      <link>Link2</link>
      <author>Author2</author>
   </post>
   <post>
      <publicationDate>2011-06-05</publicationDate>
      <title>Title1</title>
      <description>Description1</description>
      <link>Link1</link>
      <author>Author1</author>
   </post>
</myFeed>

II. The full solution

This can be generalized to a parameterized solution:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:param name="postElements" select=
 "'|entry|item|'"/>
 <xsl:param name="pub-dateElements" select=
  "'|published|pubDate|'"/>

  <xsl:template match="node()|@*" name="identity">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*" mode="identity"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="/">
  <myFeed>
   <xsl:apply-templates select=
   "//*[contains($postElements, concat('|',name(),'|'))]">
    <xsl:sort order="descending" select=
     "*[contains($pub-dateElements, concat('|',name(),'|'))]"/>
   </xsl:apply-templates>
  </myFeed>
 </xsl:template>

 <xsl:template match="*">
  <xsl:choose>
   <xsl:when test=
    "contains($postElements, concat('|',name(),'|'))">
    <post>
      <xsl:apply-templates/>
    </post>
   </xsl:when>
   <xsl:when test=
   "contains($pub-dateElements, concat('|',name(),'|'))">
    <publicationDate>
     <xsl:apply-templates/>
    </publicationDate>
   </xsl:when>
   <xsl:otherwise>
    <xsl:call-template name="identity"/>
   </xsl:otherwise>
  </xsl:choose>
 </xsl:template>

</xsl:stylesheet>

This transformation can be used with infinite number of formats, just specifying all “entry” alternative names in the external (global) parameter $postElements and all “published-date” alternative names in the external (global) parameter $pub-dateElements.

Anyone can try this transformation to verify that when applied on the two XML documents above it again produces the same, wanted and correct result.