Since file-upload is handled on RR end PHP process will only receive the filename of temporary resources. This resource would not be registered in uploaded files hash and, as a result, function is_uploaded_file will always return false.
Reference: roadrunner-server/roadrunner#133
Please note that you should not use any of the following methods die, exit. Use buffered output if your library requires to write content to stdout.
Using roadrunner on Windows with WinCache extension might cause worker bytecode to stuck in memory.