ShortHex Hash generator

ShortHash.php

<?php
/**
 * Copyright 2012 Silvona Services. All Rights Reserved.
 * File Created By: Rick L Bird
 * Created TimeStamp: 9/29/12 2:39 AM
 */
namespace Silvona\Core\AppBundle\Utils;

/* KevinBurnsJr Blog - PHP Unique Hash.
 * Using a variation proposed by Ernesto on December 19th, 2011 using the PHP BC Math Library
 *  Typeout from http://blog.kevburnsjr.com/php-unique-hash
 */

class ShortHash {

  /* Next prime greater than 62 ^ n / 1.618033988749894848 */
  private static $golden_primes = array(
    1,
    41,
    2377,
    147299,
    9132313,
    566201239,
    35104476161,
    2176477521929,
    134941606358731,
    8366379594239857,
    518715534842869223
  );

  /* Ascii : 0 9, A Z, a z */
  /* $chars = array_merge(range(48,57), range(65,90), range(97,122)) */
  private static $chars = array(
    0=>48,1=>49,2=>50,3=>51,4=>52,5=>53,6=>54,7=>55,8=>56,9=>57,10=>65,
    11=>66,12=>67,13=>68,14=>69,15=>70,16=>71,17=>72,18=>73,19=>74,20=>75,
    21=>76,22=>77,23=>78,24=>79,25=>80,26=>81,27=>82,28=>83,29=>84,30=>85,
    31=>86,32=>87,33=>88,34=>89,35=>90,36=>97,37=>98,38=>99,39=>100,40=>101,
    41=>102,42=>103,43=>104,44=>105,45=>106,46=>107,47=>108,48=>109,49=>110,
    50=>111,51=>112,52=>113,53=>114,54=>115,55=>116,56=>117,57=>118,58=>119,
    59=>120,60=>121,61=>122
  );

  public static function base62($int) {
    $key = "";
    while(bccomp($int,0) > 0) {
      $mod = bcmod($int,62);
      $key .= chr(self::$chars[$mod]);
      $int = bcdiv($int,62);
    }
    return strrev($key);
  }

  public static function udihash($num, $len = 5) {
    $ceil = bcpow(62, $len);
    $prime = self::$golden_primes[$len];
    $dec = bcmod(bcmul($num,$prime),$ceil);
    $hash = self::base62($dec);
    return str_pad($hash, $len, 0, STR_PAD_LEFT);
  }


  public static function quick($len = 7) {
    $uid = self::bchexdec(uniqid());
    return self::udihash($uid,$len);
  }

  public static function bchexdec($hex) {
    if(strlen($hex) == 1) {
      return hexdec($hex);
    } else {
      $remain = substr($hex, 0, -1);
      $last = substr($hex, -1);
      return bcadd(bcmul(16, self::bchexdec($remain)), hexdec($last));
    }
  }

}

Original now uses BC math and is reversible http://blog.kevburnsjr.com/php-unique-hash