php - Does using /u modifier in PCRE cause any problemm if unicode is not used?

Question

/u modifier is used in PCRE when we use unicode characters like /x{0xFF0}.

Does it cause any problem if we have a regex like /^\d{10}$/u (e.g. using unicode modifier when unicode is not used in regex) ? I ask this because I get different results in localhost and production server(using preg_match function)

And if it doesn't cause any problem, why this modifier is not used by default?

Answer 1

它不会引起任何问题，因为 ascii 字符是 utf-8 的一部分，只是要小心，因为“u”修饰符取决于使用 --enable-utf8 编译的 PCRE。