[0] => 00
    [1] => 01
    [2] => 02
    [3] => 03
    [4] => 04
    [5] => 10
    [6] => 11
    [7] => 12
    [8] => 13
    [9] => 14
    [10] => 20
    [11] => 21
    [12] => 22
    [13] => 23
    [14] => 24
    [15] => 30
    [16] => 31
    [17] => 32
    [18] => 33
    [19] => 34
    [20] => 40
    [21] => 41
    [22] => 42
    [23] => 43
    [24] => 44

 public function getFromIndex($stringIndex, $stringLen) {
      $symbolsNum = count($this->symbols);

      $indexes = [];
      $prev = $stringIndex;

      while ($stringLen > 0) {
        $result = $prev % $symbolsNum;
        $prev = $prev / $symbolsNum;

        if (!isset($this->symbols[$result])) {
          throw new \Exception("Invalid symbol index:" + $result);
        }
        $indexes[] = $this->symbols[$result];
        $stringLen--;
      }
      $indexes = array_reverse($indexes);

      return implode("", $indexes);
    }