Google\Spreadsheet\CellEntry::getCellIdString PHP Method

    public function getCellIdString()
    {
        return sprintf("R%sC%s", $this->row, $this->column);
    }

 /**
  * Get the feed entries
  * 
  * @return array \Google\Spreadsheet\CellEntry
  */
 public function getEntries()
 {
     if (count($this->entries) > 0) {
         return $this->entries;
     }
     $postUrl = $this->getPostUrl();
     foreach ($this->xml->entry as $entry) {
         $cell = new CellEntry($entry, $postUrl);
         $this->entries[$cell->getCellIdString()] = $cell;
     }
     return $this->entries;
 }