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php – DOMElement cloning and appending: 'Wrong Document Error'

Posted by: admin April 23, 2020 Leave a comment

Questions:

There’s something I don’t fully understand about node cloning with the PHP’s DOM api. Here’s a sample file that quickly duplicates the issue I’m coming across.

$doc  = new DOMDocument( '1.0', 'UTF-8' );
$root = $doc->createElement( 'root' ); // This doesn't work either $root = new DOMElement( 'root' );
$doc->appendChild( $root );

$doc2  = new DOMDocument( '1.0', 'UTF-8' );
$root2 = $doc2->createElement( 'root2' );
$doc2->appendChild( $root2 );

// Here comes the error
$root2->appendChild( $root->cloneNode() );

When you run this little snippet an exception is thrown

Fatal error: Uncaught exception
‘DOMException’ with message ‘Wrong
Document Error’

Can I not grab a node from a document, clone it, and then append it to another document?

How to&Answers:

Use DOMDocument->importNode to import the node into the other document before adding it to the DOM.

Answer:

You’ll have to append the result of the importNode method to the DOM. Keep in mind that the method could return false when it cannot be imported

if ($importedNode = $doc2->importNode($root->cloneNode())) {
    $root2->appendChild($importedNode);
}

If you need to import the node, all of it’s child nodes (resursively) and/or the node’s attributes use the optional second parameter deep:

if ($importedNode = $doc2->importNode($root->cloneNode(), true)) {
    $root2->appendChild($importedNode);
}