code: protected function paddingStringToArray($padding)
      {
          $parts = explode(' ', $padding);
          switch (count($parts)) {
              case static::CSS_PADDING_ONE:
                  $value = (float)$parts[0];
  
                  return [$value, $value, $value, $value];
                  break;
              case static::CSS_PADDING_TWO:
                  $verticalValue = (float)$parts[0];
                  $horizontalValue = (float)$parts[1];
  
                  return [$verticalValue, $horizontalValue, $verticalValue, $horizontalValue];
              case static::CSS_PADDING_THREE:
                  $parts[3] = $parts[1];
  
                  return $parts;
              case static::CSS_PADDING:
                  return $parts;
              default:
                  throw new \InvalidArgumentException('Invalid padding format');
          }
      }
docs: Formats:
  all
  vertical horizontal
  top horizontal bottom
  top right bottom left.
  
  @param string $padding
  
  @return array