actually i know only this way...
True, as long as you're able to:
i) call a web service (an I'm sure you can do that from PHP)
ii) write an MDX query
you can get by with XMLA.
I wrote a java client that does the same 5 years ago ( http://sourceforge.net/projects/whex/ ).
Be advised, though, that you'll have to setup XMLA on the server box, but that is not a problem, check this out:
http://msdn.microsoft.com/en-us/library/cc917711.aspx
I don't know what version of AS & OS are you using, but this can be done even with the old AS 2000.
Best regards,
Igor