DOMXPath::evaluate
DOMXPath::registerNamespace
DOMXPath
PHP Manual

# DOMXPath::query

Evaluates the given XPath expression

### Description

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

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`

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

### 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`.

### Changelog

Version | Description
--- | ---
5.3.3 | The `registerNodeNS` parameter was added.

### 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 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";
}
?>`

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";
}
?>`

### See Also

- DOMXPath::evaluate