In a nuthsell, SimpleXMl has two things broken:

1. Elements that represent “emtpy” tags evaluate to false. This is weird design.
2. Other elements sometimes evaluate to false due to bugs.

I covered problem #1 in the previous post. This post is about #2.

Unfortunately, due to bugs in the SimpleXML parser, a non-empty element may evaluate to false. No version I tested is completely bug-free, and the difference between correct and incorrect behavior may be as subtle as adding a space outside the element in question.

The code I use for testing is along these lines:

$xml = $xml = simplexml_load_string($text);
$node = $xml->xpath($xpath)[0];
if ($node) echo "Evaluates to true!"; else echo "Evaluates to false!";

Here are the test results:

I believe evaluating non-null objects to false was not a good idea in the first place, but worse yet, PHP cannot really do it right, so the result of if ($node) check is never reliable.