Description:
------------
If you have a reference to an SimpleXML subtree item, you cannot change the value of that.

Reproduce code:
---------------
<?php
$xml = new SimpleXMLElement("<?xml version='1.0'?>\n"
							."<chunk>\n"
							."<item id='1'>one</item>\n"
							."<item id='2'>two</item>\n"
							."</chunk>\n"
							);

function test(& $xentry)
{
	$xentry['id'] = 22; // set id=2 to id=22, works fine
	$xentry = 'TWENTYTWO'; // !!! this line is ignored !!!
}

$xml->item[0] = 'ELEVEN'; // works
$xml->item[0]['id']=11;   // works
echo str_replace("\n", "<br>", htmlspecialchars($xml->asXML()))."<br>"; // OK, fine

// try the same with a reference -> does not work
test($xml->item[1]);
echo "<h3>After replacement:</h2>";
echo str_replace("\n", "<br>", htmlspecialchars($xml->asXML())); // error - $xentry is not an object
?>

Expected result:
----------------
...
<item id="2">two</item>

After replacement:
...
<item id="22">TWENTYTWO</item>


Actual result:
--------------
...
<item id="2">two</item>

After replacement:
...
<item id="22">two</item>