Metaphone is a phonetic algorithm published in 1990 for indexing words by their English pronunciation.
Metaphone fundamentally improves on the Soundex algorithm by using information about variations and inconsistencies in English spelling and pronunciation to produce a more accurate encoding, which does a better job of matching words and names which sound similar. As with Soundex, similar sounding words should share the same keys. Metaphone is available as a built-in operator in a number of systems, including later versions of PHP.
