DOMXPath::evaluate

(PHP 5 >= 5.1.0, PHP 7)

Evaluates the given XPath expression and returns a typed result if possible

public mixed DOMXPath::evaluate ( string $expression [, DOMNode $contextnode [, bool $registerNodeNS = true ]] )

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

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.

Returns:

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.

Changelog:

5.3.3

The registerNodeNS parameter was added.

Examples:

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";

?>

The above example will output:

There are 2 english books