使用XPath和PHP过滤XML文档

Question

I am trying to extract XML data using PHP and XPath. Consider the following XML document:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <channel>
        <item>
            <title>My Second Great Title</title>
            <link>http://server.com/content/my-second-great-title</link>
            <tag>vuluptate</tag>
            <tag>id</tag>
            <tag>cras</tag>
            <tag>pretium</tag>
            <tag>conubia</tag>
            <tag>libero</tag>
            <description>This is a second great description</description>
            <publishedAt>Sat, 08 Nov 2015 10:00:52 +0000</publishedAt>
            <isVisible>true</isVisible>
            <content>Ut luctus auctor varius. Donec vitae erat felis. Nam ac erat vulputate, consequat elit id, dictum urna. Vestibulum dignissim eget felis vitae tempor. Suspendisse molestie lectus at est accumsan, et porta sapien elementum. Vivamus pretium imperdiet nisl id consequat. Sed gravida bibendum odio, et vehicula nibh hendrerit eget. Cras sit amet semper sem. Vivamus non lorem sed ex fringilla malesuada consequat non arcu. Etiam nec sodales tortor. In scelerisque massa vitae purus suscipit consectetur. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Cras ultrices eros tortor, eu sollicitudin eros pellentesque sit amet. Integer rutrum velit eget libero efficitur, non auctor lorem rutrum. Vivamus porta dolor ut enim dapibus, nec rutrum nisi sagittis.</content>
        </item>
        <item>
            <title>My Great Title</title>
            <link>http://server.com/content/my-great-title</link>
            <tag>lorem</tag>
            <tag>ipsum</tag>
            <tag>arcu</tag>
            <tag>sic</tag>
            <description>This is a great description</description>
            <publishedAt>Sat, 08 Nov 2015 10:00:52 +0000</publishedAt>
            <isVisible>true</isVisible>
            <content>Praesent consectetur, dolor non vehicula ultrices, nisl libero feugiat ligula, ut faucibus metus arcu et dui. Curabitur eleifend feugiat posuere. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec cursus blandit lorem, ullamcorper vestibulum massa molestie non. Maecenas erat enim, pretium eget velit dapibus, consequat placerat eros. Nam vulputate nisi at urna gravida accumsan. Fusce id ultrices nunc. Aenean varius quam in tincidunt cursus. Quisque sed arcu est. Etiam dignissim, neque at maximus feugiat, turpis nunc sollicitudin eros, et lobortis enim dui sed felis. Nulla rhoncus diam porttitor ullamcorper imperdiet.</content>
        </item>
        <item>
            <title>My Title</title>
            <link>http://server.com/content/my-title</link>
            <tag>auctor</tag>
            <tag>felis</tag>
            <description>This is a simple description</description>
            <publishedAt>Sat, 05 Nov 2015 16:07:23 +0000</publishedAt>
            <isVisible>true</isVisible>
            <content>Ut luctus auctor varius. Donec vitae erat felis. Nam ac erat vulputate, consequat elit id, dictum urna. Vestibulum dignissim eget felis vitae tempor. Suspendisse molestie lectus at est accumsan, et porta sapien elementum. Vivamus pretium imperdiet nisl id consequat. Sed gravida bibendum odio, et vehicula nibh hendrerit eget. Cras sit amet semper sem. Vivamus non lorem sed ex fringilla malesuada consequat non arcu. Etiam nec sodales tortor. In scelerisque massa vitae purus suscipit consectetur. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Cras ultrices eros tortor, eu sollicitudin eros pellentesque sit amet. Integer rutrum velit eget libero efficitur, non auctor lorem rutrum. Vivamus porta dolor ut enim dapibus, nec rutrum nisi sagittis.</content>
        </item>
    </channel>
</root>

So far I have been trying to use expressions like:

//root/channel/item/title|//root/channel/item/link|//root/channel/item/tag

and unfortunately the <item> tags get lost after applying the expression, so is there a way to filter through the data preserving the item tags?

Answer 1

Your XPath-expression is correct. And it gives the correct output - that means, what you requested. You are globally(//) selecting title , link and tag element-nodes. And that's what you get out of this expression. You did not select any item element-nodes.

To filter each item-node for the three mentioned tags, you'd have to iterate over all item -nodes and filter their children (and possibly reconstruct the item -elements). Not globally filtering all three elements (//...|//...|//...).

Because you haven't given a PHP code snippet, I'll illustrate this in XSLT:

What you did:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
 <xsl:output method="xml" version="1.0" encoding="UTF-8"/>
  <xsl:template match="/">
   <xsl:copy-of select="//root/channel/item/title|//root/channel/item/link|//root/channel/item/tag" />
  </xsl:template>
 </xsl:stylesheet>

What should (probably) be done:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
 <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
 <xsl:strip-space elements="*"/>

  <xsl:template match="root">
     <xsl:element name="root">          
       <xsl:for-each select="channel">  <!-- iterating over 'channel'-nodes -->
         <xsl:element name="channel">   <!-- reconstruct 'channel'-node  -->             
          <xsl:for-each select="item">     <!-- iterating over 'item'-nodes -->
            <xsl:element name="item">      <!-- iterating over 'item'-nodes -->
              <xsl:copy-of select="title|link|tag" />    <!-- filtering each for the three elements -->
            </xsl:element>      
          </xsl:for-each>              
         </xsl:element>
       </xsl:for-each>           
     </xsl:element>
  </xsl:template>

 </xsl:stylesheet>

Answer 2

Consider an XSLT solution when needing to restructure an entire XML document. Like other general purpose languages, PHP maintains an XSLT processor. Essentially, you need to write out the nodes you do not require. Below runs an identity transform to copy entire document as is and then writes an empty template match to the nodes not needed. I include two equivalent solutions.

XSLT Script (save as .xsl or .xslt file)

<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>

  <!-- Identity Transform -->
  <xsl:template match="@*|node()">
    <xsl:copy>
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>

  <!-- SOLUTION 1-->
  <!-- <xsl:template match="description|publishedAt|isVisible|content"/> -->

  <!-- SOLUTION 2-->
  <xsl:template match="item/*[not(name()='title' or name()='link' or name()='tag')]"/>

</xsl:transform>

PHP Script

<?php

// Load the XML source and XSLT file
$doc = new DOMDocument();    
$doc->load('Input.xml');

$xsl = new DOMDocument;
$xsl->load('XSLTScript.xsl');

// Configure the transformer
$proc = new XSLTProcessor;
$proc->importStyleSheet($xsl); 

// Transform XML source
$newXml = $proc->transformToXML($doc);

// Save output to file
$xmlfile = 'Output.xml';
file_put_contents($xmlfile, $newXml);

?>

OUTPUT

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <channel>
    <item>
      <title>My Second Great Title</title>
      <link>http://server.com/content/my-second-great-title</link>
      <tag>vuluptate</tag>
      <tag>id</tag>
      <tag>cras</tag>
      <tag>pretium</tag>
      <tag>conubia</tag>
      <tag>libero</tag>
    </item>
    <item>
      <title>My Great Title</title>
      <link>http://server.com/content/my-great-title</link>
      <tag>lorem</tag>
      <tag>ipsum</tag>
      <tag>arcu</tag>
      <tag>sic</tag>
    </item>
    <item>
      <title>My Title</title>
      <link>http://server.com/content/my-title</link>
      <tag>auctor</tag>
      <tag>felis</tag>
    </item>
  </channel>
</root>