Sorry if this is a silly and/or stupid question but... Will there ever be, or would it even be possible to have a PHP.NET? Or have I got the wrong end of the stick?
The CLR is essentially a virtual machine, so things are compiled to it essentially the same way C code is compiled to x86 or PowerPC or arm or whatever.
There is an implementation of python that compiles to .NET assemblies, there's also COBOL, and a few others. No technical reason PHP couldn't be done the same and executed by the CLR in IIS.