Description:
------------
---
From manual page: http://www.php.net/class.domnode
---
The documentation states that $prefix is NULL if it is unspecified, but instead I'm getting an empty string.
This causes an annoyance when passing it through to XMLWriter::startElementNs(), as it'll output (an example) <:derp> instead of <derp>.

Test script:
---------------
<?php
$doc = new DOMDocument();
$doc->loadXML('<derp></derp>');
$root = $doc->documentElement;

echo "prefix: [$root->prefix]<br>";
echo "name: [$root->localName]<br>";
echo 'is the prefix NULL? ' . (is_null($root->prefix) ? 'yep' : 'nope');
var_dump($root);

Expected result:
----------------
prefix: []
name: [derp]
is the prefix NULL? yep

--omitted--\test.php:9:
object(DOMElement)[2]
  public 'tagName' => string 'derp' (length=4)
  public 'schemaTypeInfo' => null
  public 'nodeName' => string 'derp' (length=4)
  public 'nodeValue' => string '' (length=0)
  public 'nodeType' => int 1
  public 'parentNode' => string '(object value omitted)' (length=22)
  public 'childNodes' => string '(object value omitted)' (length=22)
  public 'firstChild' => null
  public 'lastChild' => null
  public 'previousSibling' => null
  public 'attributes' => string '(object value omitted)' (length=22)
  public 'ownerDocument' => string '(object value omitted)' (length=22)
  public 'namespaceURI' => null
  public 'prefix' => null
  public 'localName' => string 'derp' (length=4)
  public 'baseURI' => string 'file:/--omitted--/' (length=46)
  public 'textContent' => string '' (length=0)

Actual result:
--------------
prefix: []
name: [derp]
is the prefix NULL? nope

--omitted--\test.php:9:
object(DOMElement)[2]
  public 'tagName' => string 'derp' (length=4)
  public 'schemaTypeInfo' => null
  public 'nodeName' => string 'derp' (length=4)
  public 'nodeValue' => string '' (length=0)
  public 'nodeType' => int 1
  public 'parentNode' => string '(object value omitted)' (length=22)
  public 'childNodes' => string '(object value omitted)' (length=22)
  public 'firstChild' => null
  public 'lastChild' => null
  public 'previousSibling' => null
  public 'attributes' => string '(object value omitted)' (length=22)
  public 'ownerDocument' => string '(object value omitted)' (length=22)
  public 'namespaceURI' => null
  public 'prefix' => string '' (length=0)
  public 'localName' => string 'derp' (length=4)
  public 'baseURI' => string 'file:/--omitted--/' (length=46)
  public 'textContent' => string '' (length=0)