Status of undocumented language constructs

Hi there,

I'm in the process of (re)building a PHP syntax highlighter. I've been using
both the doco, the Zend lexer/parser code, and the mailing lists as my
reference, and I've been able to work out most things for myself. But I've
found a few that I can't suss.

Firstly, I can't find any descriptions of these constructs, even though Zend
recognises them:

- The "scope resolution" operator ::, which is given the endearing and
cryptic token
   T_PAAMAYIM_NEKUDOTAYIM in the lexer.
- declare
- enddeclare
- const
- use

Clearly, these aren't in common use, and not many people will suffer if I
get it wrong, but I'd still like to know:

- what version of PHP did these things appear?
- what version of PHP did they get deprecated?

Secondly, there's the status of string literals and the back-tick operator,
and whether embedded newlines are supposed to be legal. I know they work,
but are the following *supposed* to be legal, or not?

    "I am a multi
     line string"

    'So am
     I'

    `echo exec
     me`

Thanks,

Gid