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

Descrizione

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

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

Elenco dei parametri

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.

Errori/Eccezioni

The following errors are possible when using an expression that invokes PHP callbacks.

Throws an Error if a PHP callback is invoked but there were no callbacks registered, or if the named callback was not registered.
Throws a TypeError if the php:function syntax is used and the handler name is not a string.
Throws an Error if a non-DOM object was returned from a callback.

Valori restituiti

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.

Esempi

Example #1 Getting the count of all the english books

<?php

$doc = new DOMDocument;

$doc->load('examples/book-dcobook.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";

?>

Il precedente esempio visualizzerà:

There are 2 english books

Vedere anche:

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