Description:
------------
The DOM extension's DOMNode class seems to hide object properties when DOMNode objects are displayed.

For example, the following shows that print_r() presents the lastChild property as a string "(object value omitted)", but also that this property is in fact a DOMElement object when directly printed.

This affects Xdebug and makes it painful to debug the DOM extension.

https://3v4l.org/NFpRS shows that this persists in 7.3.0 alpha 1.

Test script:
---------------
<?php

$dom = new DOMDocument();
$dom->loadHTML('<h1>Configuration</h1>', LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
print_r($dom);
print_r($dom->lastChild);

Actual result:
--------------
DOMDocument Object
(
    [doctype] => 
    [implementation] => (object value omitted)
    [documentElement] => (object value omitted)
    [actualEncoding] => 
    [encoding] => 
    [xmlEncoding] => 
    [standalone] => 1
    [xmlStandalone] => 1
    [version] => 
    [xmlVersion] => 
    [strictErrorChecking] => 1
    [documentURI] => 
    [config] => 
    [formatOutput] => 
    [validateOnParse] => 
    [resolveExternals] => 
    [preserveWhiteSpace] => 1
    [recover] => 
    [substituteEntities] => 
    [nodeName] => #document
    [nodeValue] => 
    [nodeType] => 13
    [parentNode] => 
    [childNodes] => (object value omitted)
    [firstChild] => (object value omitted)
    [lastChild] => (object value omitted)
    [previousSibling] => 
    [attributes] => 
    [ownerDocument] => 
    [namespaceURI] => 
    [prefix] => 
    [localName] => 
    [baseURI] => 
    [textContent] => Configuration
)
DOMElement Object
(
    [tagName] => h1
    [schemaTypeInfo] => 
    [nodeName] => h1
    [nodeValue] => Configuration
    [nodeType] => 1
    [parentNode] => (object value omitted)
    [childNodes] => (object value omitted)
    [firstChild] => (object value omitted)
    [lastChild] => (object value omitted)
    [previousSibling] => 
    [attributes] => (object value omitted)
    [ownerDocument] => (object value omitted)
    [namespaceURI] => 
    [prefix] => 
    [localName] => h1
    [baseURI] => 
    [textContent] => Configuration
)