java d3 : in fact this opensource library offers client program and server program (in Pick BASIC for D3 right now). The first section is a collection of D3 programs that make up a socket server. The second section is devoted to client programs that can call this server. There are currently working clients for Java, PHP, COM, C#, and Python.
This forum posting includes source to access D3 from PHP using FlashCONNECT. However the server can be any process that returns a delimited string, the connectivity can be any valid pipe. So you can use the same technique to access jBase with REST, U2 with a WebService and UniObjects ... any technology of your choice.
Accessing U2 from PHP is U2-specific, but as with the above the same techniques, and code to a great extent, can be used with any MV environment.
Web Application Server: PHP to D3 : http://www.pfinders.com/phptod3/