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Date: Wed, 19 Mar 2014 16:08:35 -0700
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To: Yasuo Ohgaki <yohgaki@ohgaki.net>, PHP internals <internals@lists.php.net>, 
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Subject: default_charset and friends
From: aharvey@php.net (Adam Harvey)

Yasuo, internals, doc-friends,

I'm working on the 5.6 migration guide, and I'm a little confused
about what state the default encoding RFC actually ended up in after
it was accepted and merged. UPGRADING says:

> Changes were made to character set handling in:
>  - the iconv and mbstring extensions,
>  - and htmlentities(), htmlspecialchars(), html_entity_decode() functions
>
> The precedence for these is now:
>
>  default_charset < internal/input/output_encoding < (mbstring.* || iconv.=
*) < function parameter
>
> For example, the easiest way to use the UTF-8 encoding is to set
> default_charset=3DUTF-8 and leave the following php.ini parameters

The way this reads to me, assuming I don't have any other encoding
settings set, I should be able to set default_encoding to (for
example) "cp1252" and get Windows-1252 handling as the default in
htmlentities(), htmlspecialchars() and html_entity_decode() if I don't
specify the encoding parameter. In practice, though, that doesn't seem
to be the case. I created this script:

<?php
ini_set('default_charset', 'cp1252');

var_dump(htmlentities("\xA3", ENT_HTML5));
var_dump(htmlentities("\xA3", ENT_HTML5, 'cp1252'));

var_dump(html_entity_decode("&pound;", ENT_HTML5));
var_dump(html_entity_decode("&pound;", ENT_HTML5, 'cp1252'));
?>

And ran it using the -n option, so that anything I had set in my
php.ini would be ignored. My expected output would have been for the
two htmlentities() and html_entity_decode() calls to return the same
strings (ignore the unknown character glyphs; my terminal is UTF-8, so
I expect Windows-1252 output to be broken):

string(7) "&pound;"
string(7) "&pound;"
string(1) "=EF=BF=BD"
string(1) "=EF=BF=BD"

But instead, I got this output, suggesting that the calls without
explicit charset parameters were treated as UTF-8:

string(0) ""
string(7) "&pound;"
string(2) "=C2=A3"
string(1) "=EF=BF=BD"

What am I missing here? Do htmlentities(), htmlspecialchars() and
html_entity_decode() actually respect default_charset? (Also, if I set
internal_encoding, input_encoding and output_encoding, which one
should get used for each?)

Thanks,

Adam