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justin at NO dot blukrew dot SPAM dot com ¶
21 years ago
I originally looked at soundex() because I wanted to compare how individual letters sounded. So, when pronouncing a string of generated characters it would be easy to to distinguish them from eachother.  (ie, TGDE is hard to distinguish, whereas RFQA is easier to understand). The goal was to generate IDs that could be easily understood with a high degree of accuracy over a radio of varying quality. I quickly figured out that soundex and metaphone wouldn't do this (they work for words), so I wrote the following to help out. The ID generation function iteratively calls chrSoundAlike() to compare each new character with the preceeding characters. I'd be interested in recieving any feedback on this. Thanks.

<?php
function chrSoundAlike($char1, $char2, $opts = FALSE) {
    $char1 = strtoupper($char1);
    $char2 = strtoupper($char2);
    $opts  = strtoupper($opts);

    // Setup the sets of characters that sound alike.
    // (Options: include numbers, include W, include both, or default is none of those.)
    switch ($opts) {
    case 'NUMBERS':
        $sets = array(0 => array('A', 'J', 'K'),
                      1 => array('B', 'C', 'D', 'E', 'G', 'P', 'T', 'V', 'Z', '3'),
                      2 => array('F', 'S', 'X'),
                      3 => array('I', 'Y'),
                      4 => array('M', 'N'),
                      5 => array('Q', 'U', 'W'));
        break;

    case 'STRICT':
        $sets = array(0 => array('A', 'J', 'K'),
                      1 => array('B', 'C', 'D', 'E', 'G', 'P', 'T', 'V', 'Z'),
                      2 => array('F', 'S', 'X'),
                      3 => array('I', 'Y'),
                      4 => array('M', 'N'),
                      5 => array('Q', 'U', 'W'));
        break;
        
    case 'BOTH':
        $sets = array(0 => array('A', 'J', 'K'),
                      1 => array('B', 'C', 'D', 'E', 'G', 'P', 'T', 'V', 'Z', '3'),
                      2 => array('F', 'S', 'X'),
                      3 => array('I', 'Y'),
                      4 => array('M', 'N'),
                      5 => array('Q', 'U', 'W'));
        break;

    default:
        $sets = array(0 => array('A', 'J', 'K'),
                      1 => array('B', 'C', 'D', 'E', 'G', 'P', 'T', 'V', 'Z'),
                      2 => array('F', 'S', 'X'),
                      3 => array('I', 'Y'),
                      4 => array('M', 'N'),
                      5 => array('Q', 'U'));
        break;
    }
    
    // See if $char1 is in a set.
    $matchset = array();
    for ($i = 0; $i < count($sets); $i++) {
        if (in_array($char1, $sets[$i])) {
            $matchset = $sets[$i];
        }
    }

    // IF char2 is in the same set as char1, or if char1 and char2 and the same, then return true.
    if (in_array($char2, $matchset) OR $char1 == $char2) {
        return TRUE;
    } else {
        return FALSE;
    }
}
?>
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