$objPHPExcel->setActiveSheetIndex(0)
    ->setCellValue('A1', 'Field Name');
    
$objPHPExcel->getActiveSheet()->getColumnDimension('A')->setWidth(50);

$columnArray    = array("A","B","C","D","E","F","G","H");
    
$objPHPExcel->setActiveSheetIndex(0)
->setCellValueExplicit("A", VALUE, PHPExcel_Cell_DataType::TYPE_STRING)