Read XLS in PHP using PhpSpreadsheet

<?php
require 'vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

$spreadsheet = new Spreadsheet();

$inputFileType = 'Xlsx';
$inputFileName = './mysheet.xlsx';

/**  Create a new Reader of the type defined in $inputFileType  **/
$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);
/**  Advise the Reader that we only want to load cell data  **/
$reader->setReadDataOnly(true);

$worksheetData = $reader->listWorksheetInfo($inputFileName);

foreach ($worksheetData as $worksheet) {

$sheetName = $worksheet['worksheetName'];

echo "<h4>$sheetName</h4>";
/**  Load $inputFileName to a Spreadsheet Object  **/
$reader->setLoadSheetsOnly($sheetName);
$spreadsheet = $reader->load($inputFileName);

$worksheet = $spreadsheet->getActiveSheet();
print_r($worksheet->toArray());

}

I would check with your Client to see if they are using real Excel or some other spreadsheet.

If they are using some other spreadsheet and exporting using a "Export as Excel" functionality that may explain why its not being recognised by PHPSpreadsheet as any of the possible valid excel formats.

In which case, and depending what is in the spreadsheet, it may be worth asking them to export their spreadsheet as a csv (comma delimited values) file, as that is such a simple format it should be a valid output. You could then read it using fgetcsv() function calls instead of having to use PHPSpreadsheet.