Description:
------------
The DOM function "getElementByTagName" doesn't work properly when it's call from an element.
The W3C specification say "Returns a NodeList of all DESCENDANT Elements with a given tag name, in the order in which they are encountered in a preorder traversal of this Element tree."
But getElementByTagName return ALL elements encountered after the current element and not only the descendant elements in the tree...

Reproduce code:
---------------
<?php
$xml = '<?xml version="1.0"?>
<config><section id="section1">
	<param name="param1">value1</param>
	<param name="param2">value2</param>
</section>
<section id="section2">
	<param name="param3">value3</param>
</section>
</config>';

$dom = new DomDocument;
$dom -> loadXML($xml);
$params = $dom -> documentElement -> firstChild -> getElementsByTagName('param');

foreach ($params as $param) {
	echo $param -> getAttribute('name').'<br />';
}
?>

Expected result:
----------------
param1
param2

(according with the W3C specifications)

Actual result:
--------------
param1
param2
param3