Alphanumeric Increment a string in PHP (To a certain length)

Question

I need to generate a sequence (or function to get a \"next id\") with an alphanumeric incrementor.

The length of the string must be defineable, and the Characters mu

Answer 1

I was interested in the more general solution to this problem - i.e. dealing with arbitrary character sets in arbitrary orders. I found it easiest to first translate to alphabet indexes and back again.

function getNextAlphaNumeric($code, $alphabet) {

  // convert to indexes
  $n = strlen($code);
  $trans = array();
  for ($i = 0; $i < $n; $i++) {
     $trans[$i] = array_search($code[$i], $alphabet);
  }

  // add 1 to rightmost pos
  $trans[$n - 1]++;

  // carry from right to left
  $alphasize = count($alphabet);
  for ($i = $n - 1; $i >= 0; $i--) {
     if ($trans[$i] >= $alphasize) {
       $trans[$i] = 0;
       if ($i > 0) {
         $trans[$i -1]++;
       } else {
         // overflow
       }
     }
  }

  // convert back
  $out = str_repeat(' ', $n);
  for ($i = 0; $i < $n; $i++) {
     $out[$i] = $alphabet[$trans[$i]];
  }

  return $out;
}

$alphabet = array();
for ($i = ord('0'); $i <= ord('9'); $i++) {
  $alphabet[] = chr($i);
}
for ($i = ord('A'); $i <= ord('Z'); $i++) {
  $alphabet[] = chr($i);
}

echo getNextAlphaNumeric('009', $alphabet) . "\n";
echo getNextAlphaNumeric('00Z', $alphabet) . "\n";
echo getNextAlphaNumeric('0ZZ', $alphabet) . "\n";