Parsing php manual docbook xml-files

I want to parse the php manual source files (xml docbook format) and convert them into a MySQL database. I am currently trying to do this using simpleXML extension but when I do all the entitites like &reftitle.description; and $false; raise a warning (undefined) and the script stops with "Fatal error: Uncaught exception 'Exception' with message 'String could not be parsed as XML'"
When I remove all entities form the file it parses fine, but then the information is no longer complete. I am no xml expert but I assume I need to include some reference to these entities so the parser recognizes them? I failed to find how to do this?

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