In this post from the SitePoint PHP Blog, Harry Fuecks talks about a new package of software he's worked up to make it possible for PHP to handle UTF-8 encoded strings - PHP UTF-8.

Been messing around with bits of this code for a long time, in fact since first really getting to grips with Dokuwiki, but finally got the first release out.

PHP UTF-8 is intended to make it possible to handle UTF-8 encoded strings in PHP, without requiring the mbstring extension (although it uses mbstring if it's available). In short, it provides versions of PHP's string functions (pretty much everything you'll find on this list), prefixed with utf_ and aware of UTF-8 encoding (that 1character >= 1 byte). It also gives you some tools to help check UTF-8 strings for "well formedness", strip bad sequences and some "ASCII helpers".

He continues the post, mentioning where some of the code for it was pulled from and a note about the documentation (there, but scarce). He also includes a warning for the use of it - not to use it "blindly" and only to use it when you need it, not to replace the standard PHP str_* functions.