5.5.14.txt

$ php -v
PHP 5.5.14 (cli) (built: Jul 23 2014 16:08:06) (DEBUG)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
    with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2014, by Zend Technologies
    with Xdebug v2.2.5, Copyright (c) 2002-2014, by Derick Rethans
$ php -d zend.multibyte=1 -d zend.script_encoding='EUC-JP' aa.php
PHP Warning:  Unexpected character in input:  ' in /tmp/aa.php on line 11
PHP Warning:  Unexpected character in input:  ' in /tmp/aa.php on line 11
PHP Warning:  Unexpected character in input:  ' in /tmp/aa.php on line 11
string(6) "EUC-JP"
HELLO?
[Wed Jul 23 18:25:04 2014]  Script:  '/tmp/aa.php'
/tmp/php-build/source/5.5.14/ext/mbstring/mbstring.c(612) :  Freeing 0x7FFC340E65D0 (181 bytes), script=/tmp/aa.php
=== Total 1 memory leaks detected ===

5.6.sh.0RC2.txt

$ php -v
PHP 5.6.0RC2 (cli) (built: Jul 23 2014 16:50:25) (DEBUG)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.6.0-dev, Copyright (c) 1998-2014 Zend Technologies
    with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2014, by Zend Technologies
    with Xdebug v2.2.5, Copyright (c) 2002-2014, by Derick Rethans
$ php -d zend.multibyte=1 -d zend.script_encoding='EUC-JP' aa.php
PHP Parse error:  syntax error, unexpected '"', expecting variable (T_VARIABLE) or ${ (T_DOLLAR_OPEN_CURLY_BRACES) or {$ (T_CURLY_OPEN) in /tmp/aa.php on line 10

aa.php

<?php
declare(encoding='UTF-8');

var_dump(ini_get('zend.script_encoding'));

// あ
// い
// う

echo "HELLO?\n";

aa.php は UTF-8
5.5.14 だと 過食、 5.6.0RC2 だと減食。