code: public function setLength($newLength, $padding = ' ')
      {
          $newLength     = (int) $newLength;
          $currentLength = $this->length();
  
          if ($newLength != $currentLength) {
              while ($newLength > $this->length()) {
                  $this->string .= $padding;
              }
              if ($newLength < $this->length()) {
                  $this->string = mb_substr($this->string, 0, $newLength, $this->encoding);
              }
          }
  
          return $this;
      }
docs: Set the length of this sequence.
  
  If the sequence is shorter, than it will be pad with spaces.
  
  @param int    $newLength The new length.
  @param string $padding   The padding sequence.
  
  @return StringBuilder