Why are PHP string functions not multi-byte safe by default?

问题

Why are the PHP multi-byte string functions (the ones which start with mb_) not used by default in PHP?

回答1:

Backwards compatibility. Old PHP scripts depend on non-multibyte functionality.

See also: http://www.php.net/manual/en/mbstring.overload.php

回答2:

Because non-multibyte functions were there first.

来源：https://stackoverflow.com/questions/12716064/why-are-php-string-functions-not-multi-byte-safe-by-default