(PHP 5 >= 5.2.0, PHP 7)
DOMNode::C14N — Canonicalize nodes to a string
$exclusive
[, bool $with_comments
[, array $xpath
[, array $ns_prefixes
]]]] )Canonicalize nodes to a string
exclusiveEnable exclusive parsing of only the nodes matched by the provided xpath or namespace prefixes.
with_commentsRetain comments in output.
xpathAn array of xpaths to filter the nodes by.
ns_prefixesAn array of namespace prefixes to filter the nodes by.
Returns canonicalized nodes as a string or FALSE on failure
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 );
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>"
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!
