Please find attached a thoroughly improved php.xml mode file.
I've been using this at work and home now for a long time and have tried to keep in sync with the patches to the php.xml file from jEdit SVN.
Because there are a lot of changes, I will provide the new file rather than a patch.
If necessary, I can put a list together of things that have been improved.
There's only one regression I'm aware of currently: internal PHP functions or e.g. "empty()" do not get highlighted as KEYWORD1 anymore, but just like any function. This is caused, because now e.g. "foo ()" also gets correctly handled as a function. IIRC there has been a fix/suggestion posted in the bug tracker for this - so this could get fixed without changing jEdit's syntax parser.
This mode requires jEdit 4.3pre10 (SVN trunk).
I will keep this tracker item up-to-date with the latest version.
To test/use it, copy it into ~/.jedit/modes/ and create/change ~/.jedit/modes/catalog to actually use it (take a look at the "catalog" file in jEdit's "modes" directory in the program folder).