How feasible is it for Microsoft to transition to XML-based formats for Excel files, and how would this impact PHP developers working with Excel documents?

Microsoft transitioning to XML-based formats for Excel files is feasible as they have already introduced XML-based formats like XLSX. This transition would impact PHP developers working with Excel documents as they would need to adjust their code to read and write data in the new XML format instead of the older binary format. However, PHP libraries like PHPExcel and PHPSpreadsheet already support reading and writing XML-based Excel files, making the transition smoother for developers.

// Example code using PHPSpreadsheet to read data from an XML-based Excel file
require 'vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\IOFactory;

$spreadsheet = IOFactory::load('example.xlsx');

$worksheet = $spreadsheet->getActiveSheet();

$data = $worksheet->toArray();

print_r($data);