Calculate the metaphone key of a string

# metaphone

(PHP 4, PHP 5, PHP 7, PHP 8)

metaphone — Calculate the metaphone key of a string

### Description

metaphone(string `$string`, int `$max_phonemes` = 0): string

Calculates the metaphone key of `string`.

Similar to soundex() metaphone creates the same key for similar sounding words. It's more accurate than soundex() as it knows the basic rules of English pronunciation. The metaphone generated keys are of variable length.

Metaphone was developed by Lawrence Philips <lphilips at verity dot com>. It is described in ["Practical Algorithms for Programmers", Binstock & Rex, Addison Wesley, 1995].

### Parameters

`string`

  The input string.

`max_phonemes`

  This parameter restricts the returned metaphone key to `max_phonemes` characters in length. However, the resulting phonemes are always transcribed completely, so the resulting string length may be slightly longer than `max_phonemes`. The default value of `0` means no restriction.

### Return Values

Returns the metaphone key as a string.

### Changelog

Version | Description
--- | ---
8.0.0 | The function returned `false` on failure.

### Examples

Example #1 metaphone() basic example

`<?php
var_dump(metaphone('programming'));
var_dump(metaphone('programmer'));
?>`

The above example will output:

    string(7) "PRKRMNK"
    string(6) "PRKRMR"

Example #2 Using the `max_phonemes` parameter

`<?php
var_dump(metaphone('programming', 5));
var_dump(metaphone('programmer', 5));
?>`

The above example will output:

    string(5) "PRKRM"
    string(5) "PRKRM"

Example #3 Using the `max_phonemes` parameter

In this example, metaphone() is advised to produce a string of five characters, but that would require to split the final phoneme (`'x'` is supposed to be transcribed to `'KS'`), so the function returns a string with six characters.

`<?php
var_dump(metaphone('Asterix', 5));
?>`

The above example will output:

    string(6) "ASTRKS"

### See Also

- levenshtein() - Calculate Levenshtein distance between two strings
- similar_text() - Calculate the similarity between two strings
- soundex() - Calculate the soundex key of a string

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