[php-langspec][PR #234] - Define encoding of PHP scripts (Fix #233)

You can view the Pull Request on github:
https://github.com/php/php-langspec/pull/234

Comment by IMSoP:
This is all completely the opposite of how PHP works. There is no requirement that source files be encoded in an ASCII-compatible encoding, nor is the grammar of the language defined in terms of bytes. See my comment under #233.

The only cases where we should talk about bytes is when discussing the contents of strings at run time, which are indeed arrays of bytes in no particular encoding.