Doesn't make that much sense to me - the JVM is complex and has disadvantages (slow startup times etc.), so if you can compile PHP to native code, why compile to interpreted/JIT-compiled code instead? You're just wasting cycles again.

The advantages of the Java ecosystem can be accessed through Thrift if necessary, but the C/C++ world is far from being dead.

It might be interesting for the security and debugging aspects of the JVM, but that's a bit meagre for such an effort.