impl conv string -> array key
impl conv string -> array key

- has to convert string with number to numeric key

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