<?php
$xml = new SimpleXMLElement('<tag></tag>');
echo 'An empty SimpleXMLElement is ';
var_dump((bool) $xml);
echo "\n";
$xml = new SimpleXMLElement('<tag>data</tag>');
echo 'A SimpleXMLElement with data is ';
var_dump((bool) $xml);
echo "\n";
$obj = new stdClass();
echo 'An empty stdClass is ';
var_dump((bool) $obj);