Description:
------------
---
From manual page: https://php.net/function.xml-parse
---
If xml_parse tries to parse XML containing <X xmlns="something">, it sees that "something" doesn't start with "http://" or "https://", so xml_parse returns 0; however, xml_get_error_code also returns 0 ("No error"). This only happens when parsing in fragments near that bad XML namespace.

Test script:
---------------
<?php
class XMLProcessor
{
    public function test()
    {
        $bad_xmlns = true;
        $parser = xml_parser_create_ns('UTF-8');
        xml_set_object($parser, $this);
        $success = xml_parse($parser, '<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><X xmlns="'.($bad_xmlns ? '' : 'http://').'example.org"><', false);
        $code = xml_get_error_code($parser);
        $error = xml_error_string($code);
        echo "xml_parse returned $success, xml_get_error_code = $code, xml_error_string = $error\r\n";
        $success = xml_parse($parser, 'Y>', false);
        $code = xml_get_error_code($parser);
        $error = xml_error_string($code);
        echo "xml_parse returned $success, xml_get_error_code = $code, xml_error_string = $error\r\n";
    }
}
(new XMLProcessor())->test();

Expected result:
----------------
xml_parse returned 1, xml_get_error_code = 0, xml_error_string = No error
xml_parse returned 0, xml_get_error_code = {some number), xml_error_string = {some description}

Actual result:
--------------
xml_parse returned 1, xml_get_error_code = 0, xml_error_string = No error
xml_parse returned 0, xml_get_error_code = 0, xml_error_string = No error