This is not a bug, but your test.php code stands a little in the way to see that directly. See the following example:

<pre>
<?php
$doc = new DOMDocument();
$doc->loadXML('<element attr="value"/>');
$element = $doc->documentElement;
foreach ($element->attributes as $name => $attr) {
$attr; 1 == 1; ### TOGGLE BREAKPOINT ON THIS LINE ###
echo $name, ' schemaTypeInfo: ', $attr->schemaTypeInfo;
}
</pre>

The important part is: xdebug evaluates the variables if there is a breakpoint. And you actually want that despite the warning in this case. Because $attr is an object all it's known properties are looked into, including $attr->schemaTypeInfo which gives you this standard warning - as the next line shows because it triggers it with and without xdebug.

So when you run over this or similar problems, please double check what is causing the warning specifically.

http://lxr.php.net/xref/PHP_5_4/ext/dom/attr.c#248

Duplicated with 913, which works just fine for me. I've committed a test case.