While PHP's internationalization extension offers excellent and extensive functionality for dealing with human languages, character encodings, and various related things, it is not always available. Moreover, its character decoder does not yield the same results as WHATWG's Encoding standard, making it unsuitable for implementing parsers for URLs or HTML. The more widely used multi-byte string extension not only suffers the same problems, but is also very slow.

Included here is a complete suite of WHATWG-compatible seekable string decoders which are reasonably performant while requiring no external dependencies or PHP extensions. Where applicable, code point encoders are also included. In time it may also provide other character-centric internationalization functionality.