In what ways can PHP be integrated with existing Excel files to facilitate collaborative editing while ensuring data integrity and security?

To integrate PHP with existing Excel files for collaborative editing while ensuring data integrity and security, you can use PHPExcel library to read, write, and manipulate Excel files. By setting up a web interface with PHP, users can upload, edit, and download Excel files securely. Additionally, implementing authentication and permission controls can help regulate access to the Excel files.

// Include PHPExcel library
require_once 'PHPExcel/Classes/PHPExcel.php';

// Load existing Excel file
$excelFile = 'path/to/excel/file.xlsx';
$excelObj = PHPExcel_IOFactory::load($excelFile);

// Perform necessary edits on the Excel file
$sheet = $excelObj->getActiveSheet();
$sheet->setCellValue('A1', 'New Value');

// Save the changes back to the Excel file
$writer = PHPExcel_IOFactory::createWriter($excelObj, 'Excel2007');
$writer->save($excelFile);