International PHP Conference Munich 2024

DOMNode::C14N

(PHP 5 >= 5.2.0, PHP 7, PHP 8)

DOMNode::C14NCanonicalize nodes to a string

Beschreibung

public DOMNode::C14N(
    bool $exclusive = false,
    bool $withComments = false,
    ?array $xpath = null,
    ?array $nsPrefixes = null
): string|false

Canonicalize nodes to a string

Parameter-Liste

exclusive

Enable exclusive parsing of only the nodes matched by the provided xpath or namespace prefixes.

withComments

Retain comments in output.

xpath

Ein Array von XPath-Ausdrücken, nach denen die Knoten gefiltert werden. Jeder Eintrag in diesem Array ist ein assoziatives Array mit

  • dem erforderlichen Schlüssel query, der den XPath-Ausdruck als Zeichenkette enthält.
  • dem optionalen Schlüssel namespaces, der ein Array enthält, das Namensraum-Präfixe (Schlüssel) auf Namensraum-URIs (Werte) abbildet.

nsPrefixes

An array of namespace prefixes to filter the nodes by.

Rückgabewerte

Returns canonicalized nodes as a stringBei einem Fehler wird false zurückgegeben.

Beispiele

Beispiel #1 Example with XPath query

This example demonstrates advanced usage canonicalizing and filtering the nodes by an XPath query.

<?php

$dom
= new DOMDocument();
$dom->loadXML(<<<XML
<root xmlns:food="urn:food">
<!-- redundant namespace declaration will be canonicalized -->
<food:fruit xmlns:food="urn:food">Apple</food:fruit>
<food:fruit>Orange</food:fruit>
<food:fruit>Pear</food:fruit>
<!-- vegetables here -->
<food:vegetable>Lettuce</food:vegetable>
</root>
XML);

echo
$dom->C14N(true, false, [
"query" => ".//f:fruit|.//f:fruit/text()",
"namespaces" => ["f" => "urn:food"],
]);
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

<food:fruit>Apple</food:fruit><food:fruit>Orange</food:fruit><food:fruit>Pear</food:fruit>

Siehe auch

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User Contributed Notes 3 notes

up
21
Rijk
11 years ago
When working with (malformed) HTML, you're probably better off using DOMDocument's saveHTML() method instead. C14N() will attempt to make your HTML valid XML, for example by converting <br> to <br></br>.

So instead of:
$html = $Node->C14N();

Use:
$html = $Node->ownerDocument->saveHTML( $Node );
up
16
jorda at edpsciences dot org
9 years ago
C14N() returns an empty string if the node is not included in the document tree:
<?php
$d
= new DOMDocument('1.0');
$d->loadXML('<foo></foo>');
$n = $d->createElement('bar');
var_dump($n->C14N());
$d->documentElement->appendChild($n);
var_dump($n->C14N());
?>
output:
string(0) ""
string(11) "<bar></bar>"
up
3
lordbaco
8 years ago
[edit by nielsdos: This has been fixed starting in PHP 8.4]

Good to know:

<< Due to a known issue in XML canonicalization in PHP, processing large metadata files in SimpleSAMLphp takes a big amount of resources, with that amount growing approximately by the square of the number of entities in the metadata set >>
https://simplesamlphp.org/metaprocessing

<< The C14N() function appears to have a runtime that is O(N^2) (or possibly worse?) depending on input size, which means that it becomes very slow as the input grows. For example, an input with around 196000 nodes takes about 290 seconds, while an input with 486000 nodes takes 2200 seconds. >>
https://bugs.php.net/bug.php?id=53655

We had the same issue with a 4.1 MB XML (105k lines). The sample code of ticket #53655 takes 1h36 minute to canonicalize it!
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