> Your isspace() example could simply be called utf8_isspace() because you still need to know what was inputted was utf8 anyway.
Oh yes, let's hardcode everything to use utf8, and force everyone to use it. That's much better than supporting a wide range of character sets, being flexible, and allowing people to load their existing files without running their entire hard drive through recode, remastering all their CDs and DVDs, and proxying every website they look at.
Not to mention perhaps people want to read an existing SJIS formatted text file when the system they're using defaults to UTF-8. So now you have two encodings to worry about. Are you going to keep your calls to utf8_isspace and sjis_isspace straight? Or will you go insane encoding and decoding manually at every step instead of using plain and SIMPLE Unicode in the backend, and setting input_encoding and output_encoding flags for the I/O subsystem?