Correct Answer: soundex() The soundex() function calculates the soundex key of a string A soundex key is a four character long alphanumeric string that represent English pronunciation of a word he soundex() function can be used for spelling applications < ?php $str = "hello"; echo soundex($str); ? > metaphone() The metaphone() function calculates the metaphone key of a string A metaphone key represents how a string sounds if said by an English speaking person The metaphone() function can be used for spelling applications < ?php echo metaphone("world"); ? >