code: public function getSortedCoordinates()
      {
          $sortKeys = [];
          foreach ($this->getCoordinates() as $coord) {
              sscanf($coord, '%[A-Z]%d', $column, $row);
              $sortKeys[sprintf('%09d%3s', $row, $column)] = $coord;
          }
          ksort($sortKeys);
  
          return array_values($sortKeys);
      }
docs: Get a sorted list of all cell coordinates currently held in the collection by row and column.
  
  @return string[]