Fix UKRAINIAN LETTERS I in CP866

[vstavskyi]

No description provided.

[nielsdos]

Thanks for your contribution.
Please note that you need to target the lowest supported bugfix branch as a target. So in your case that means the branch named PHP-8.1, not PHP-8.0.28 (also not PHP-8.1.x, just PHP-8.1). We can then merge it upwards to all versions that need the patch.

[youkidearitai]

As PHP 8.1 or newer, replaced to ext/mbstring/libmbfl/filters/mbfilter_singlebyte.c.

[vstavskyi]

@youkidearitai
More complicated patch is needed for mbfilter_singlebyte.c

[youkidearitai]

I have a question. I'm sorry if irrelevant. Because I don't know well to Ukrainian.
Code page 866 seems isn't include U+0406 and U+0456 from Wikipedia CP866 page.

I saw Ukrainian and Belarusian variants, calls CP1125, CP866U and CP866NAV or RUSCII. These character code include U+0406 and U+0456.
Unfortunately, PHP mbstring isn't include these character codes.

Should we add these characters codes?

[vstavskyi]

Ukraininan letters i looks like Latin letters i
but they're missing in CP866
Wikipedia Ukrainian alphabet

$s = "\u{0406}\u{0456}";
mb_convert_encoding($s, 'CP866');

result 0x3F 0x3F
with my patch result 0x49 0x69

[youkidearitai]

Ukrainian letters i looks like Latin letters i but they're missing in CP866

@vstavskyi You said that "CP866 not convert Ukrainian letters i". However, character encoding is based on character set. CP866 is not include Ukrainian letters i. Therefore, that means can't convert to Ukrainian letters i.

I think CP866 is incomplete character encoding judging from Ukrainian.

[vstavskyi]

Thank you.