DOMXPath::query

(PHP 5, PHP 7, PHP 8)

DOMXPath::query — Evaluates the given XPath expression

Description

public DOMXPath::query(string $expression, ?DOMNode $contextNode = null, bool $registerNodeNS = true): mixed

Executes the given XPath expression.

Parameters

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: Whether to automatically register the in-scope namespace prefixes of the context node to the DOMXPath object. This can be used to avoid needing to call DOMXPath::registerNamespace() manually for each in-scope namespaces. When a namespace prefix conflict exists, only the nearest descendant namespace prefix is registered.

Return Values

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.

Examples

Example #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 start 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";
}
?>

The above example will output:

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";
}
?>

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User Contributed Notes 18 notes

down

128

kkez at example dot com ¶

14 years ago

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.

down

Hayley Watson ¶

17 years ago

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'>".

down

nicolas_rainardNOSPAM at yahoo dot fr ¶

17 years ago

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...

down

RiKdnUa at mail dot ru ¶

11 years ago

Пример XPath запроса к XML документу. XML документ содержить элементы с именами из НЕлатинских символов (кириллица). При использовании в XPath запросе предиката, функция DOMXPath::query() выдает предупреждение и запрос не работает. Чтобы запрос работал, надо явно указывать ось. Файл этого примера должен быть в кодировке WINDOWS-1251. Тестировал в PHP 5.2.9-2 и PHP 5.2.17

Example XPath-query to the XML-document. XML-document contains an elements with the names of non-Latin characters (cyrillic). When used predicate in XPath-query, function DOMXPath::query() gives a warning and query does not work. In order to earned the query, it is necessary to explicitly specify the axis. The file of this example is to be in the encoding WINDOWS-1251. Tested in PHP 5.2.9-2 and PHP 5.2.17
<?php
ini_set("display_errors","on");
error_reporting(-1);
function utf8encode($str){return iconv('WINDOWS-1251', 'UTF-8', $str);}
$xml="<?xml version='1.0' encoding='WINDOWS-1251'?>
<часть>
<ссылка href='yandex.com'>Яндекс</ссылка>
<ссылка href='rik.dn.ua/fotopan.php'>г.Донецк</ссылка>
</часть>
";
$document=new domDocument();
$document->preserveWhiteSpace=false;
$document->loadXML($xml);
$domxpath=new domXpath($document);
$list=$domxpath->query(utf8encode('/child::часть/child::ссылка'));//Ok
echo '$list->length='.$list->length."\n<br/>\n";
$list=$domxpath->query(utf8encode('/часть/ссылка'));//Ok
echo '$list->length='.$list->length."\n<br/>\n";
$list=$domxpath->query(utf8encode('/child::часть/child::ссылка[position()=1]'));//Ok
echo '$list->length='.$list->length."\n<br/>\n";
$list=$domxpath->query(utf8encode('/часть/ссылка[1]'));//Warning: DOMXPath::query() [domxpath.query]: Invalid expression in ...
echo '$list->length='.$list->length."\n<br/>\n";
$list=$domxpath->query(utf8encode('/часть/ссылка[position()=1]'));//Warning: DOMXPath::query() [domxpath.query]: Invalid expression in ...
echo '$list->length='.$list->length."\n<br/>\n";
?>

down

Nibinaear ¶

16 years ago

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);

?>

down

jakob dot voss at nichtich dot de ¶

19 years ago

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>";
?>

down

jbarnett at flowershopnetwork dot com ¶

17 years ago

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.

down

adam dot prall at thinkingman dot com ¶

16 years ago

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.

down

chris dot russo99 at gmail dot com ¶

8 years ago

If you can't find a solution for PHP XPATH case sensitivity, you can always try this approach:

http://fsockopen.com/php-programming/your-final-stop-for-php-xpath-case-insensitive

Instead of inserting PHP functions into a XPATH object, convert the XPATH object into an Array(), and then use any PHP function, the regular way.

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ikmahesh at cdac dot in ¶

9 years ago

The parameters for $xPath->query() method is case sensitive. 
It matches IDs exact words.

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-1

Anonymous ¶

15 years ago

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');

?>

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-1

ondrej dot fischer at 4internet dot cz ¶

17 years ago

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.

down

-1

Niklas ¶

16 years ago

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).']');

?>

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-1

clochix at clochix dot net ¶

17 years ago

If you want to perform queries on XHTML documents, you must fix a default namespace:



<?php

$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");

?>

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-1

info at syncgw dot com ¶

13 years ago

A warning to all PHP programmer using this function PHP 5.0.0.0: We needed an equivalent to upper-case() function (is not available in XPath 1.0).

XML-Document:

<Rec>
<SourceRef>./c:calendar2</SourceRef>
<SourceRef>./c:calendar</SourceRef>
</Rec>

using 

query('//DataStore[translate(SourceRef,"abcdefghijklmnopqrstuvwxyz","ABCDEFGHIJKLMNOPQRSTUVWXYZ")="./C:CALENDAR"]/.')

returns ZERO matches.

If you change XML-Source to

<Rec>
<SourceRef>./c:calendar</SourceRef>
<SourceRef>./c:calendar2</SourceRef>
</Rec>

everything works fine

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-1

chris AT cmbuckley DOT co DOT uk ¶

13 years ago

To help with the problem where the default namespace is not registered with the DOMXPath object, you can use the following replacement to update your paths accordingly:



<?php



$xml = <<<EOS

<root xmlns="urn:test">

    <foo>bar</foo>

</root>

EOS;



$expression = '//foo';

$prefix = 'fakeprefix';



$doc = new DOMDocument();

$doc->loadXML($xml);



$context = $doc->documentElement; // or whichever element you choose

$xpath = new DOMXPath($doc);



// register namespace as below, and apply a regex to the expression

if (null !== $context->namespaceURI) {

    $xpath->registerNamespace($prefix, $context->namespaceURI);

    $expression = preg_replace('#(::|/\s*|\A)(?![/@].+?|[a-z\-]+::)#', '$1' . $prefix . ':$2', $expression);

    var_dump($expression); // string(16) "//fakeprefix:foo"

}



$foo = $xpath->query($expression, $context)->item(0);

var_dump($doc->saveXML($foo)); // string(14) "<foo>bar</foo>"



?>

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-2

yuriscom at gmail dot com ¶

13 years ago

I hope it will be helpful for someone:



I spent some time to solve the problem when you query a string with quotes inside. 



Suppose you have:

$parameter = "aaa \"bbb\"";

$domxpath->query("//path[text()=\"".$parameter."\""];



In versions > 5.3.0 there is registerPhpFunctions where you can put an addslashes. But in older version you cannot do it in simple way.



So the solution is to use a concat function. So when you have a substring with " inside, wrap it with '. And when you have a substring with ', then wrap with in ".



The code is:



<?php

$dom = new DOMDocument;

$dom->loadXML("<name>'bla' \"bla\" bla</name>");

$xpath = new DOMXPath($dom);

$nodeList = $xpath->query("//name[text()=concat(\"'bla' \" ,'\"bla\"' ,\" bla\")]");

?>



Below is the function that receives a string and returns a concat pattern for the xpath query.



<?php

    function getPattern_MQ($pattern) {

        // initiating an array of substrings

        $ar = array();

        // points to the current position in a string

        $offset = 0;

        $strlen = strlen($pattern);

        while (true) {

            // find a position of quotes

            $qPos = strpos($pattern, "\"", $offset);

            

            if (!$qPos) {

                // no more quotes

                $leftOver = $offset - $strlen;

                if ($leftOver < 0) {

                    $string = substr($pattern, $leftOver);

                    $ar[] = "\"" . $string . "\"";

                }

                break;

            }

            // add the whole substring before the quotes into the array

            $ar[] = "\"" . substr($pattern, $offset, ($qPos - $offset)) . "\"";

            // add the quotes wrapped with single quot

            $ar[] = "'" . substr($pattern, $qPos, 1) . "'";

            $offset = $qPos + 1;

        }

        // join the array to get: concat("aaa",'"',"bbb",'"');

        $pattern = "concat(''," . join(",", $dynamicPatternsAr) . ")";

        return $pattern;

    }

?>

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-2

Eric Hanson ¶

19 years ago

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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DOMXPath::query

Description

Parameters

Return Values

Examples

See Also

Found A Problem?

User Contributed Notes 18 notes