Description:
------------
DOMNode should have a property like $exists to check if the node still exists. This would be useful to avoid the "Node no longer exists" warning.

We should be able to do something like

$node->parentNode->removeChild($node);

if($node->exists)
{
  // use node ..
}

Reproduce code:
---------------
$doc = DOMDocument::loadXML('<doc><x><a>1</a></x><x><a>1</a><y><a>1</a><a>0</a></y></x></doc>');

$nodes = $doc->getElementsByTagName('a');
$nodesToRemove = array();

foreach($nodes as $node)
{
  if($node->nodeValue == 1)
  {
     $nodesToRemove[] = $node;
     $node->parentNode->removeChild($node);
  }
}

foreach($nodesToRemove as $node)
{
  $node->parentNode->removeChild($node);
}

Expected result:
----------------
This is more of a feature request. I expect to change the last loop to something like

foreach($nodesToRemove as $node)
{
  if($node->exists)
  {
    $node->parentNode->removeChild($node);
  }
}