Bug #78767 [Opn->Nab]: mb_convert_case with lower option have error with Turkish capital Ä°

Edit report at https://bugs.php.net/bug.php?id=78767&edit=1 ID: 78767 Updated by: requinix@php.net Reported by: meminaydin at cmbilisim dot com -Summary: mb_convert_case with lower option have error +Summary: mb_convert_case with lower option have error with Turkish capital İ -Status: Open +Status: Not a bug Type: Bug Package: mbstring related Operating System: Debian PHP Version: 7.3.11 Block user comment: N Private report: N New Comment: First, a glossary: - 0x69 is the Latin 'i' (U+0069 LATIN SMALL LETTER I) - 0xCC87 is a "combining dot above" (U+0307 COMBINING DOT ABOVE) Some links: - https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML009/0619.html - http://www.i18nguy.com/unicode/turkish-i18n.html - https://www.nu42.com/2017/02/for-your-eyes-only.html And some Unicode rules: - Turkish 'İ' (capital 'I' with dot) is uppercase of Latin 'i' (lowercase 'i' with dot) - Latin 'I' (capital 'I' without dot) is uppercase of Turkish 'ı' (lowercase 'i' without dot) - Latin 'i' followed by any "above" diacritical mark means that it loses its normal dot and gains the mark instead If lowercasing Turkish 'İ' produced Latin 'i' (0x69), then uppercasing it would produce Latin 'I'. That is incorrect: the dot was lost. By appending the combining dot, lowercasing produces something that is still visually Latin 'i' but uppercasing can correctly identify that it should produce the Turkish 'İ' with dot... however it's not actually possible to know that it should be literally *that* 'İ' (U+0130) because codepoints don't indicate language, so instead the uppercase is Latin 'I' with another combining dot. https://3v4l.org/eWIep Previous Comments: ------------------------------------------------------------------------ [2019-10-31 20:27:08] meminaydin at cmbilisim dot com Description: ------------ mb_convert_case with lower option have a bug. If the string being converted contains turkish capital i (İ), the output is incorrect. No problem in versions 7.2 and earlier. Test script: --------------- <?php $str = 'yİy'; echo $tmp = mb_convert_case($str, MB_CASE_LOWER, 'UTF-8'), "\n"; echo implode('', unpack('H*', $tmp)), "\n"; Expected result: ---------------- yiy 796979 Actual result: -------------- yi̇y 7969cc8779 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78767&edit=1