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Base62 Encode / Decode

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If you have large integers and you want to shrink them down in size for whatever reason, you can use this code. Should be easy enough to extend if you want even higher bases (just add a few more chars and increase the base).

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  1. function encode($val, $base=62, $chars='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') {
  2.     // can't handle numbers larger than 2^31-1 = 2147483647
  3.     $str = '';
  4.     do {
  5.         $i = $val % $base;
  6.         $str = $chars[$i] . $str;
  7.         $val = ($val - $i) / $base;
  8.     } while($val > 0);
  9.     return $str;
  10. }
  11.  
  12. function decode($str, $base=62, $chars='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') {
  13.     $len = strlen($str);
  14.     $val = 0;
  15.     $arr = array_flip(str_split($chars));
  16.     for($i = 0; $i < $len; ++$i) {
  17.         $val += $arr[$str[$i]] * pow($base, $len-$i-1);
  18.     }
  19.     return $val;
  20. }
  21.  
  22. echo encode(2147483647); // outputs 2lkCB1

URL: http://programanddesign.com/php/base62-encode/

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