Why are PHP string functions not multi-byte safe b

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.