Description:
------------
See test script below.

The strangest behavior is the difference between a pure ASCII string and an UTF-8 with chars in the [80-FFFF] range.

The other wrong thing is the difference of behavior between substr() and grapheme_substr(). I think substr's behavior is the good one.

Test script:
---------------
<?php

var_dump(substr('deja', 1, -4));
var_dump(substr('deja', -1, 0));
var_dump(grapheme_substr('deja', 1, -4));
var_dump(grapheme_substr('deja', -1, 0));
var_dump(grapheme_substr('déjà', 1, -4));
var_dump(grapheme_substr('déjà', -1, 0));

?>


Expected result:
----------------
bool(false)
string(0) ""
bool(false)
string(0) ""
bool(false)
string(0) ""


Actual result:
--------------
bool(false)
string(0) ""
bool(false)
string(0) ""
string(5) "éjà"
bool(false)