string implementation

[solidpulse]

I thought implementing string would be easy, but I was so wrong,
[https://github.com/avierr/graalphp/commit/58142efd3c8e3e65ac1be93d21edea32c35c9810]

PHP supports string interpolation,
probably this needs some pre-processing to convert it into string concatenation operations?

we know Java uses strings that are utf16 encoded.
strings in PHP are also used to store binary data, I went ahead and did some research on how others handle this,

1.PeachPie
https://github.com/peachpiecompiler/peachpie/blob/master/src/Peachpie.Runtime/PhpString.cs

2.JPHP
https://github.com/jphp-group/jphp/blob/master/jphp-runtime/src/php/runtime/memory/StringMemory.java

3.HippyVM
https://github.com/hippyvm/hippyvm/blob/master/hippy/objects/strobject.py

4.Tagua-vm
https://github.com/tagua-vm/tagua-vm (not sure how this works)

other challenges:
implicit casting rules that PHP has to convert strings to numbers and vis versa.
https://php.net/manual/en/language.types.type-juggling.php

Most of this is way out of my league, so I don't have any opinions on this, let me if anyone has any thoughts on which direction to proceed in

[Girgias]

Note: the behaviour of numeric string is changing in PHP 8: https://wiki.php.net/rfc/saner-numeric-strings

The php spec repo hasn't been updated yet.