1--TEST-- 2Serialize non-default but empty xmlns 3--EXTENSIONS-- 4dom 5--FILE-- 6<?php 7 8$dom = Dom\XMLDocument::createFromString('<test xmlns="urn:a"><a:child xmlns:a=" "/></test>'); 9 10echo $dom->saveXml(), "\n"; 11 12?> 13--EXPECTF-- 14Warning: Dom\XMLDocument::createFromString(): xmlns:a: ' ' is not a valid URI in Entity, line: 1 in %s on line %d 15<?xml version="1.0" encoding="UTF-8"?> 16<test xmlns="urn:a"><a:child xmlns:a=" "/></test> 17