The [documentation here](https://www.php.net/manual/en/class.domdocument.php#domdocument.props.xmlstandalone) says that xmlStandalone defaults to false when missing, but the following test fails on **PHP 8.1***: ```php public function testThatStandaloneDefaultsToFalse(): void { $doc = new \DOMDocument(); $doc->loadXML('<?xml version="1.0" encoding="US-ASCII"?><root/>'); $this->assertFalse($doc->xmlStandalone); } ``` \* I haven't tried it on other PHP versions and 3v4l.org sadly misses `DOMDocument`..