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The DOMXPath class

<<DOMXPath::evaluate

DOMXPath::registerNamespace>>

DOMXPath::query

(PHP 5)

DOMXPath::query Evaluates the given XPath expression

Beschreibung

DOMNodeList DOMXPath::query ( string $expression [, DOMNode $contextnode [, boolean $registerNodeNS = true ]] )

Executes the given XPath expression.

Parameter-Liste

expression

The XPath expression to execute.

contextnode

The optional contextnode can be specified for doing relative XPath queries. By default, the queries are relative to the root element.

registerNodeNS

The optional registerNodeNS can be specified to disable automatic registration of the context node.

Rückgabewerte

Returns a DOMNodeList containing all nodes matching the given XPath expression. Any expression which does not return nodes will return an empty DOMNodeList.

If the expression is malformed or the contextnode is invalid, DOMXPath::query() returns FALSE.

Changelog

Version Beschreibung
5.3.3 The registerNodeNS parameter was added.

Beispiele

Beispiel #1 Getting all the english books

<?php

$doc 
= new DOMDocument;

// We don't want to bother with white spaces
$doc->preserveWhiteSpace false;

$doc->Load('book.xml');

$xpath = new DOMXPath($doc);

// We starts from the root element
$query '//book/chapter/para/informaltable/tgroup/tbody/row/entry[. = "en"]';

$entries $xpath->query($query);

foreach (
$entries as $entry) {
    echo 
"Found {$entry->previousSibling->previousSibling->nodeValue}," .
         
" by {$entry->previousSibling->nodeValue}\n";
}
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

Found The Grapes of Wrath, by John Steinbeck
Found The Pearl, by John Steinbeck

We can also use the contextnode parameter to shorten our expression:

<?php

$doc 
= new DOMDocument;
$doc->preserveWhiteSpace false;

$doc->load('book.xml');

$xpath = new DOMXPath($doc);

$tbody $doc->getElementsByTagName('tbody')->item(0);

// our query is relative to the tbody node
$query 'row/entry[. = "en"]';

$entries $xpath->query($query$tbody);

foreach (
$entries as $entry) {
    echo 
"Found {$entry->previousSibling->previousSibling->nodeValue}," .
         
" by {$entry->previousSibling->nodeValue}\n";
}
?>

Siehe auch

  • DOMXPath::evaluate() - Evaluates the given XPath expression and returns a typed result if possible.


13 BenutzerBeiträge:
- Beiträge aktualisieren...
kkez at example dot com
3.09.2010 16:51
If the query() function seems to ignore your $contextnode, and instead returns all the tags in the document, try to use a relative path (use a . in front of the query):

<?php
    $xml
= "<?xml version='1.0' encoding='UTF-8'?>
        <test>
            <tag1>
                <uselesstag>
                    <tag2>test</tag2>
                </uselesstag>
            </tag1>
            <tag2>test2</tag2>
        </test>"
;
  
   
$dom = new DomDocument();
   
$dom->loadXML($xml);
   
$xpath = new DomXPath($dom);
  
   
$tag1 = $dom->getElementsByTagName("tag1")->item(0);
  
    echo
$xpath->query("//tag2")->length; //output 2 -> correct
   
echo $xpath->query("//tag2", $tag1)->length; //output 2 -> wrong, the query is not relative
   
echo $xpath->query(".//tag2", $tag1)->length; //output 1 -> correct (note the dot in front of //)
?>

See that i couldn't use $xpath->query("tag2", $tag1) as per the documentation, since "tag2" is not a direct child of "tag1".
I don't know why this note was deleted, i just tested it and it's correct.
It's not a bug, it's simply not written in the documentation.
Anonymous
27.11.2009 21:26
I found this useful for building page templates

<?php
$xsl
= new DOMDocument;
$xsl->load('layout.xsl');

// Set the <xsl:include> href attribute, the inner stylesheet to include in this layout
$xpath = new DomXPath($xsl);
$res = $xpath->query('//xsl:include');
$res->item(0)->setAttribute('href','page.xsl');
$xsl->save('media/xsl/layout.xsl');
?>
Niklas
27.08.2008 23:36
For XPath escaping use the following method (of course it could be more efficient).
<?php
public function xpathescape($string)
{
$result = 'concat(';

for(
$i=0, $j=strlen($string); $i<$j; ++$i)
{
if(
$i > 0)
$result .= ",";

if(
$string[$i] == '\'')
$result .= "\"".$string[$i]."\"";
else
$result .= '\''.$string[$i].'\'';
}

$result .= ')';

return
$result;
}
?>

Use it this way:
<php
$xpath->query('//example[sub='.xpathescape($acomplexstring).']');

?>
adam dot prall at thinkingman dot com
20.07.2008 6:01
If you're wondering, like I was, why your XPath queries are not returning any of the new DOMElements you create in your (X)HTML documents, and only the ones originally loaded in with (for example) loadXML(), this is why; if you're doing things right, you have registered the nameSpace 'html' after creating your DOMXPath object thus:

<?php

class XPathQueryLength {
     private
$nameSpace = '';
     function
__construct(DOMDocument $doc) {
         
$this->xpath = new DOMXPath($this->doc);
         
$this->xpath->registerNamespace(
                
'html','http://www.w3.org/1999/xhtml' );
     }
     function
queryLength($query) {
          return
$this->xpath->query($query)->length;
     }
}

?>

...but don't forget that when adding new elements to the above DOMDocument $doc, to use createElementNS() instead of createElement(), otherwise you'll have this problem:

<?php

//$doc is a previously loaded XHTML document containing a normal html, head and body structure
//$body is the first selected tag using $doc->getElementsByTagName('body');

$pTag = $doc->createElement('p','This is a new paragraph!');
$body->appendChild($pTag);

$xPath = new XPathQueryLength($doc);
print
$xPath->queryLength('//html:p');

output: 0

print $xPath->queryLength('//p');

output: 1

?>

So do this instead:

<?php

//$doc is a previously loaded XHTML document containing a normal html, head and body structure
//$body is the first selected tag using $doc->getElementsByTagName('body');

$pTag = $doc->createElementNS('http://www.w3.org/1999/xhtml','p','This is a new paragraph!');
$body->appendChild($pTag);

$xPath = new XPathQueryLength($doc);
print
$xPath->queryLength('//html:p');

output: 2

print $xPath->queryLength('//p');

output: 0

?>

The resulting XHTML file from both example scripts looks much like this:

<html>
  <head></head>
  <body>
     <p>This is a hardcoded paragraph.</p>
     <p>This is a new paragraph!</p>
  </body>
</html>

...so you would think that a paragraph is a paragraph is a paragraph, since you never see the prefix, as in "<html:p>This is a new paragraph!</html:p>".

This may seem glaringly obvious, but I was writing a class that converts CSS queries into XPath queries, and the fact that a namespace had been registered was rather buried in the code.

We love the DOM, the DOM is good to us.
Nibinaear
3.03.2008 15:15
I've searched the entire web looking for a way to update / modify/ change/ alter the elements of an xml file and found NOTHING!

So here it is, the defninitive way to "Change XML elements with PHP" rather than adding / appending new ones. This uses XPATH:

<?php

// Create a DOMDocument instance
$xml = new DOMDocument;

// Ignore whitespace between nodes (default: true)
$xml->preserveWhiteSpace = false;

$file='about.xml';

// Load the XML data source
$xml->Load($file);

$xpath = new DOMXPath($xml);

$query='/regions/branch';

$entries = $xpath->query($query);

foreach (
$entries as $entry)
{
 
$entry->firstChild->nodeValue="like this!";
  echo
$entry->firstChild->nodeValue
}

$xml->save($file);

?>
ondrej dot fischer at 4internet dot cz
25.10.2007 15:46
Unfortunately PHP's DOM extension doesn't support use of:
<?xml-stylesheet type="text/xsl" ... ?>
processing instruction.
Here is an example, how to implement it using XPath query and extending DOMDocument by a method output().

<?php

// This simple function adds missing direct usage of anonymous instances
// in PHP5's reference model
function a($var) {
   return
$var;
}

// Extended DOMDocument class
class MyDOMDocument extends DOMDocument
{

   public function
output()
   {
     
$stylesheets = array();
     
$PIs = a(new DOMXPath($this))
                  ->
query('/processing-instruction("xml-stylesheet")');

      foreach(
$PIs as $PI)
      {
        
// This might be implemented cleaner by regular parsing
         // of DOMProcessingInstruction::data property
        
if(ereg('type *= *"text/xsl" +href *= *"([^"]+)"', $PI->data, $mem))
         {
           
// Here should be verified, that XSL file exists.
           
a($stylesheets[] = new DOMDocument())->load($mem[1]);
         }
      }

      if(
$stylesheets)
      {
        
$processor = new XSLTProcessor();
         foreach(
$stylesheets as $stylesheet)
           
$processor->importStylesheet($stylesheet);
         return
$processor->transformToDoc($this);
      }
     
// If no stylesheet instructions present, return self directly
     
else return $this;

   }
}

?>

Usage:

<?php

$document
= new MyDOMDocument();
$document->load('my.xml');
echo
$document->output()->saveXML();

?>

With following file my.xml:

<?xml version="1.0" ?>
<?xml
-stylesheet type="text/xsl" href="my.xsl" ?>
<my-root />

and existing file my.xsl that code will transform the xml file using my.xsl and output the result.
jbarnett at flowershopnetwork dot com
11.09.2007 22:46
The order of nodes in the return value is not guaranteed.

When my code was on an old server, the returned DOMNodeList was in document order.  On the new server, the returned DOMNodeList is in a consistent order, but it is not in document order. 

PHP passes this function call off to the xmlXPathEvalExpression() function in libxml.  That function in libxml only accepts two arguments - the same two this PHP function accepts.  There must have been a change in the libxml version from the old server to the new server, and that libxml behaves differently.

This would be okay if PHP had a way to compare nodes so I can resort the nodes manually, but there is not.

So, there is no guaranteed way to get an ordered list of nodes like DOM 3 XPath provides.
Hayley Watson
13.08.2007 2:43
Note that if your DOMDocument was loaded from HTML, where element and attribute names are case-insensitive, the DOM parser converts them all to lower-case, so your XPath queries will have to as well; '//A/@HREF' won't find anything even if the original HTML contained "<A HREF='example.com'>".
nicolas_rainardNOSPAM at yahoo dot fr
10.07.2007 11:04
Please note that what clochix says is valid for *any* document which has a default namespace (as it is the case for XHTML).

This document :

<?xml version="1.0" encoding="UTF-8" ?>

<root xmlns="http://www.exemple.org/namespace">

    <element id="1">
    ...
    </element>

    <element id="2">
    ...
    </element>

</element>

must be accessed this way :

$document = new DOMDocument();
$document->load('document.xml');

$xpath = new DOMXPath($document);
$xpath->registerNameSpace('fakeprefix', 'http://www.exemple.org/namespace');

$elements = $xpath->query('//fakeprefix:element');

Of course, there is no prefix in the original document, but the DOMXPath class *needs* one, whatever it is, if you use a default namespace. It *doesn't work* if you specify an empty prefix like this :

$xpath->registerNameSpace('', 'http://www.exemple.org/namespace');

Hope this help to spare some time...
clochix at clochix dot net
1.03.2007 13:05
If you want to perform queries on XHTML documents, you must fix a default namespace:

$doc = new DOMDocument;
$doc->preserveWhiteSpace = true;
$doc->resolveExternals = true; // for character entities
$doc->load("http://www.w3.org/");
$xpath = new DOMXPath($doc);
// won't work
$entries = $xpath->query("//div");
// you should use :
$xpath->registerNamespace("html", "http://www.w3.org/1999/xhtml");
$entries = $xpath->query("//html:div");
ckrack at i-z dot de
23.12.2005 4:27
tried finding a node by it's text content?

// Get all elements that equal the string "test"
$query = "//*[.='test']";
jakob dot voss at nichtich dot de
14.11.2005 9:33
You can transform the result nodes into new DOMDocument objects this way:

<?php
$result
= $xpath->query($query);
$resultNode = $result->item(0);
$newDom = new DOMDocument;
$newDom->appendChild($newDom->importNode($resultNode,1));

print
"<pre>" . htmlspecialchars($newDom->saveXML()) . "</pre>";
?>
Eric Hanson
13.07.2005 2:40
Two great XPath references follow.

XPath in Five Paragraphs (finally!):
http://www.rpbourret.com/xml/XPathIn5.htm

The w3c spec actually has a bunch of helpful examples:
http://www.w3.org/TR/xpath#location-paths



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