- * Turkish has two different i, one with a dot and another without a dot. They
- * are totally different letters in this language, so we have to override the
+ * The Turkish language, like other Turkic languages, distinguishes
+ * a dotted letter 'i' from a dotless letter 'ı' (U+0131 LATIN SMALL LETTER DOTLESS I).
+ * In these languages, each has an equivalent uppercase mapping:
+ * ı (U+0131 LATIN SMALL LETTER DOTLESS I) -> I (U+0049 LATIN CAPITAL LETTER I),
+ * i (U+0069 LATIN SMALL LETTER I) -> İ (U+0130 LATIN CAPITAL LETTER I WITH DOT ABOVE).
+ *
+ * Unicode CaseFolding.txt defines this case as type 'T', a special case for Turkic languages:
+ * tr and az. PHP 7.3 parser ignores this special cases. so we have to override the