"'<anychar>", each of which acts as a flag,
- is optionally followed by a width specification: a nonempty digit
sequence,
- - is optionally followed by '.' and a precision specification: a nonempty
- digit sequence,
+ - is optionally followed by '.' and a precision specification: an [optional?]
+ nonempty digit sequence,
+ (It's optional per <https://www.php.net/manual/en/function.sprintf.php>,
+ but this is actually buggy: <https://github.com/php/php-src/issues/18897>.)
- is optionally followed by a size specifier 'l', which is ignored,
- is finished by a specifier
- 's', that needs a string argument,