Get the 32-bit CRC code for a string in base 62 (0-9A-Za-z)

str_crc62.php

<?php

/**
 * Get the 32-bit CRC code for a string in base 62
 *
 * @param string $str The string to get the CRC for
 * @param array $chars Optional. An array mapping the integer keys 0-61 to distinct characters. 
 *                     If not supplied, the character for each value will be calculated on the fly.
 * @return string The base 62 CRC code
 */
function str_crc62($str, $chars = null){
    // Get the CRC code for the string
    $crc = intval(sprintf('%u', crc32($str)));
    $crc62 = '';

    // Convert CRC from base 10 to base 62 (0-9A-Za-z)
    do{
        // Get the mod of the current CRC
        $m = $crc%62;
        
        // Convert the mod value to a character and add it to the 
        if($chars !== null)
            $crc62 = $chars[$m].$crc62;
        else
            $crc62 = chr((($m>35)?61:(($m>9)?55:48))+$m).$crc62;
        
        // Set the CRC to the integer division value
        $crc = ($crc-$m)/62;
    } while($crc > 0);
    
    return $crc62;
}

// Generate the character map
$chars = array();
for($m = 0; $m < 62; $m++){
    $chars[$m] = chr((($m>35)?61:(($m>9)?55:48))+$m);
}

// Both should return '2ygOVa'
str_crc62('*_TeSt.StRiNg_*', $chars);
str_crc62('*_TeSt.StRiNg_*');