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I found a previously asked question here, and am trying to implement Eineki's solution, however I'm on a 32bit system (I've installed Ubuntu 20.04 on an old laptop for testing). It was noted in the comments that the code wouldn't work on a 32bit system but there are workarounds, but they are not spelled out clearly enough for me. Unfortunately I'm pretty new with PHP and also with this website. I tried to comment there to ask for help and was told I couldn't because my account is new.

So here's how I modified that code, based on the instructions given in those comments. The instructions were:

Try to change the line occurence of $num % $b with fmod($num, $b) and $num/$b (and similar ones) with intdiv($nub, $b).

function base10to62($num, $b=62) {
  $base='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
  $r = fmod($num  % $b) ;
  $res = $base[$r];
  $q = floor(intdiv($num/$b));
  while ($q) {
    $r = fmod($q % $b);
    $q = floor(intdiv($q/$b));
    $res = $base[$r].$res;
  }
  return $res;
}

function base62to10( $num, $b=62) {
  $base='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
  $limit = strlen($num);
  $res=strpos($base,$num[0]);
  for($i=1;$i<$limit;$i++) {
    $res = $b * $res + strpos($base,$num[$i]);
  }
  return $res;

$base3_string1 = "212012222102200121211101010110220202222222211121102101011101111110021111210000102211101010101110101010101010220110000110111010101010000010002020001010200000022111111111110011120201111110000002002002002001011011101010000110010000000000";
$base10test = base_convert($base3_string1, 3, 10);
$base62test = base10to62($base10test);
$base62returntest = base62to10($base62test);

echo ("My base3_string1 is: ".$base3_string1."<br>");
echo ("My base10 number is: ".$base10test."<br>");
echo ("My base62 number is: ".$base62test."<br>");
echo ("My base62return hash is: ".$base62returntest."<br>");

As you can see, I have a base3 number I'm converting to base10. I'm doing this because it looks like Eineki's function wants base10 input. The base10 number I'm trying to convert is 8080064204040204462880280000286008662604880682228402402248426842, but when I attempt this the return is 0 and when I try to change it back of course the result is 0 because the input is 0.

I'm guessing I've misinterpreted Eineki's instructions on how to convert his code to work on a 32bit system. If anyone can help me correct this it would be appreciated.

emailsbecker
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  • Does this answer your question? [converting a number base 10 to base 62 (a-zA-Z0-9)](https://stackoverflow.com/questions/4964197/converting-a-number-base-10-to-base-62-a-za-z0-9) – Omar Tammam Apr 10 '22 at 14:08
  • @OmarTammam obviously not, as the OP referenced the same SO article at the beginning of his question. – cyberbrain Apr 10 '22 at 14:35
  • @Omar - no, as cyberbrain pointed out, that was the thread I linked to above. Can one of you ask Eineki to come look at my question? I can't comment on that thread, nor do I see a way to PM him. – emailsbecker Apr 21 '22 at 16:34

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