I haven't seen this issue with eZ Publish, yet, but know this problem from my other application experience when those were deployed at some egzotic servers, especially non-linux. I have no idea yet how eZ Publish takes care of the environment variables, it would take some looking into. My own solution, or rather prevention, has always been an initial layer which would "translate" and/or "fix" the environment into PHP variables, and only those were later used in the application. If I had to move to another server that is not fully compatible, I would look around and see what environment vars are available to arrange for what my application requires.
Of course that's a bit risky and you may have to go deep into modifications... it also requires understanding of what this PATH should return and what CAN substitute for that!
I hope someone can provide you with some additional information on this. Good luck.
