[maoxor]

With the default singleQuote: false, a single-quoted string is turned into a double-quoted one when it has no escape sequences. The check only counted a valid \u{...} code point as an escape, but PHP treats any \u{ in a double-quoted string as the start of one and refuses to parse the file when it isn't valid.

PHPUnit's Sanitizer has

static fn (array $matches) => sprintf('\u{%04X}', mb_ord($matches[0], 'UTF-8')),

which was printed as sprintf("\u{%04X}", ...), and php -l then fails with Invalid UTF-8 codepoint escape sequence. Symfony's CliDumper and HtmlDumper hit the same thing with '\u{'.strtoupper(dechex(...)).'}'.

Any \u{ now keeps the string as it is. I added these cases to tests/string-double-quote/quoting.php; the snapshot showed "\u{%04X}", "\u{" and "\u{zz}" before the change. yarn test (including the standalone build), AST_COMPARE=1 yarn test:node and yarn lint pass, and the three files above format to valid PHP again.

[Dextheking1]

checked this one. the fix is right: without it the formatter flips the three new cases to double quotes, where they are invalid escapes. ran tests/string-double-quote on this branch, passes. put the old regex back and the snapshot fails on exactly those three cases. looks good.