Description:
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As I noted in Request #65364, when loading an XML document from memory (string, 
file, whatever), such as via DOMDocument::loadXml(), PHP tells libxml to use a 
particular default value as the base URI, and this value is then exposed through 
the baseURI property in the DOM.

It's quite possible that the XML has been cached or otherwise came from 
somewhere that's known, and the app will want to use a particular URL as the 
base URI at parse time. It would be nice, then, when the app does get around to 
parsing, for it to see the same baseURI properties as if DOMDocument::load() had 
been used with the original URL.

So, regardless of what the default base URI is, PHP should provide a way to 
override it at parse time. I suggest allowing loadXml() to take another 
argument: a string for the base URI.

This will help with using the baseURI property for what is ostensibly its 
purpose: resolving relative URI references in the document, such as href values 
in XHTML documents and Atom feeds.