Visually editing PHP’s Docbook manuals

Having put off writing documentation for Image_Transform for too long (which I realised today when I came to write a program and couldn’t remember the API) I’ve been looking around at visual Docbook editors available for free. Here’s two I’ve found so far:

* “Morphon”:http://www.morphon.com/xmleditor/index.shtml
* “XMLmind Standard Edition”:http://www.xmlmind.com/xmleditor/stdedition.html

Both edit their own DocBook samples perfectly; neither will open PEAR’s documentation without errors.

Morphon says:
@FatalError at file file://localhost/C:/code/peardoc/en/preface.xml[line 18,column 27]: The entity “url.docbook.xml” was referenced, but not declared.@

XMLmind won’t even open the file, kicking up the error:
@parse error in “file:/C:/code/peardoc/en/preface.xml”, linke 18, column 9: reference to undefined entity “url.docbook.xml”@

How do I get these entities to be referenced? Obviously I’m missing something, but I’ve found nothing I understand in the documentation to fix the problem.