Description:
------------
The manual page for DOMNode::removeChild() states:

"After calling this method, the DOMNode::$namespaceURI property on the parent 
node will be reset to NULL. Above example shows how to work around it."

http://www.php.net/manual/en/domnode.removechild.php

The example recommends storing the old value of $parentNode->namespaceURI and 
restoring it after the removeChild() call. IMHO this sounds more like something 
that should be fixed rather than documented, but more to the point, I could not 
reproduce it on several different PHP versions. On the contrary, the recommended 
solution throws the error "Cannot write property".

It appears that this has been fixed in a past version.

Related bug: https://bugs.php.net/bug.php?id=53083

Test script:
---------------
$xml = '<?xml version="1.0" encoding="UTF-8"?>'
     . '<b:book xmlns:b="urn:irrelevant">'
     .    '<b:chapter>Once upon a time</b:chapter>'
     . '</b:book>';

$doc = new DOMDocument();
$doc->loadXML($xml);

$book = $doc->documentElement;
$chapter = $book->getElementsByTagName("chapter")->item(0);
echo "book nsURI before: ", $book->namespaceURI, "\n";
  // prints "book nsURI before: urn:irrelevant"

$nsuri = $book->namespaceURI;
$book->removeChild($chapter);
echo "book nsURI after: ", $book->namespaceURI, "\n";
  // prints "book nsURI after: urn:irrelevant"

// fails with "Cannot write property"
//$book->namespaceURI = $nsuri;