如何将工作表的列数设为整数(28)，而不是精确性字母(“AB”)?

Given:

考虑到:

$this->objPHPExcelReader = PHPExcel_IOFactory::createReaderForFile($this->config['file']);
$this->objPHPExcelReader->setLoadSheetsOnly(array($this->config['worksheet']));
$this->objPHPExcelReader->setReadDataOnly(true);
$this->objPHPExcel = $this->objPHPExcelReader->load($this->config['file']);
$this->objPHPExcelReader = PHPE