Description:
------------
When assigning values to node parameters, entities are not escaped, however when reading values, the entities are replaced by their meaning.

i.e. assigning and reading behave assymetric.

Suggestion: Add escaping of values that are assigned.

Kind of workaround: Use htmlspecialchars() manually on values before assigning. (This workaround will not work for ')

Reproduce code:
---------------
<?php
$rawxml = '<root par="F" />';
$test = 'A &quot; B';

$rr = simplexml_load_string($rawxml);

header("Content-Type: text/plain");

echo($rr["par"]);
echo("\n");
echo("\n");

$rr["par"] = $test;

echo($rr->asXML());
echo("\n");

echo($rr["par"]);
echo("\n");
?>

Expected result:
----------------
F

<?xml version="1.0"?>
<root par="A &quot;quot; B"/>

A &quot; B

Actual result:
--------------
F

<?xml version="1.0"?>
<root par="A &quot; B"/>

A " B