Dom namespacenode improvement

[veewee]

This PR makes DOMNamespaceNode extend from DOMNode.
This allows for easier data access without having to worry about all possible types all the times:

<hello xmlns="http://www.hello.com" xmlns:foo="http://foo">
    <item xmlns:bar="http://bar">A</item>
</hello>

Given following example,
The result can either be DOMAttr|DOMNamespaceNode|false:

$xmlns = $hello->getAttributeNode('xmlns');
$foo = $hello->getAttributeNode('xmlns:foo');

(Since the xmlns attributes are very hidden away in the dom extension, you'll need to directly fetch it based on exact attribute name.)

Meaning that if you want to use the result of a the getAttributeNode(),
you might always have to keep in mind the possibility of it being a DOMNameSpaceNode:

function doSomethingWithAttribute(DOMAttr | DOMNamespaceNode $node)
{
    // do something
}

If you are dealing with only one function, this might be OK.
But if you were to build a library around DOM, this becomes quite messy and it works clumsy.

A better solution is to - at least - make DOMNamespaceNode extends DOMNode.
This way you can at least use the base type:

function doSomethingWithAttribute(DOMNode $node)
{
    return match(true) {
        $node instanceof DOMAttr => 'attr',
        $node instanceof DOMNameSpaceNode => 'xmlns attribute',
    };
}

This PR is in line with the java jaxon implementation:
http://www.cafeconleche.org/jaxen/apidocs/org/jaxen/dom/NamespaceNode.html

An alternative solution might to make it extend DOMAttr. However, I don't think this is the way to go, since you can also fetch the namespaces through xpath. In this case it would make less sense for it to be an attribute:

$namespaces = $xpath->query('./namespace::*', $node);

[nikic]

cc @beberlei

[veewee]

@beberlei : Saw your comment in #6936 (comment)

there are a bunch of thing sin ext/dom just to make libxml happy, for example DOMNameSpaceNode not being a DOMNode and others.

Can you give me an example in how libxml wouldnt be happy about this? Haven't found any erroneous cases myself yet.

Ran testcases on 2 repo's without any libxml specific problems:

• https://github.com/veewee/xml
• https://github.com/phpro/soap-client

(Both contain quite some namespaces, but none of them contain really big XML files)

[ramsey]

What can you do with a DOMNameSpaceNode? It doesn't appear to have any methods or properties.

[veewee]

@ramsey It contains a representation of an xmlns namespace attribute:

<hello xmlns:test="http://test" />

var_dump($doc->documentElement->getAttributeNode('xmlns:test'));

object(DOMNameSpaceNode)#90 (8) {
      ["nodeName"]=>
      string(10) "xmlns:test"
      ["nodeValue"]=>
      string(11) "http://test"
      ["nodeType"]=>
      int(18)
      ["prefix"]=>
      string(4) "test"
      ["localName"]=>
      string(4) "test"
      ["namespaceURI"]=>
      string(11) "http://test"
      ["ownerDocument"]=>
      string(22) "(object value omitted)"
      ["parentNode"]=>
      string(22) "(object value omitted)"
    }

[nikic]

@beberlei : Saw your comment in #6936 (comment)

there are a bunch of thing sin ext/dom just to make libxml happy, for example DOMNameSpaceNode not being a DOMNode and others.

Can you give me an example in how libxml wouldnt be happy about this? Haven't found any erroneous cases myself yet.

I'd be interested in that as well. I found this discussion on internals: https://externals.io/message/104687