compiler: conv. to string (fix)
compiler: conv. to string (fix)

ref https://github.com/peachpiecompiler/peachpie/issues/936

iolevel/peachpie-concept,iolevel/peachpie-concept,peachpiecompiler/peachpie,peachpiecompiler/peachpie,peachpiecompiler/peachpie,iolevel/peachpie-concept