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# DOMXPath->query()

(no version information, might be only in CVS)

DOMXPath->query() -- Evaluates the given XPath expression

## 说明

class DOMXPath {
DOMNodeList query ( string expression [, DOMNode contextnode] )
}

Executes the given XPath `expression`.

## 参数

`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.

## 返回值

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

## 范例

例 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";
}
?>`

上例将输出：

    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";
}
?>`

## 参见

DOMXPath->evaluate()

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