DOMXPath::evaluate

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

DOMXPath::evaluate — Evaluates the given XPath expression and returns a typed result if possible

说明

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

Executes the given XPath expression and returns a typed result if possible.

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.

registerNodeNS

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

返回值

Returns a typed result if possible or a DOMNodeList containing all nodes matching the given XPath expression.

If the expression is malformed or the contextNode is invalid, DOMXPath::evaluate() returns false.

范例

示例 #1 Getting the count of all the english books

<?php

$doc = new DOMDocument;

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

$xpath = new DOMXPath($doc);

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

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

$entries = $xpath->evaluate($query, $tbody);
echo "There are $entries english books\n";

?>

以上例程会输出：

There are 2 english books

参见