PHPOffice/PhpSpreadsheet

<?php
include_once 'include/bootstrap.php'; // Adjust bootstrap to your environment.
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;
print "[".date("Y-m-d H:i:s",time())."] Start Data Population.\n";
$spreadsheet = new Spreadsheet();
$spreadsheet->setActiveSheetIndex(0);
$columnLookup = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; // Limit to 26 columns
//$numberOfRows = 2500; // Takes Seconds
//$numberOfRows = 25000; // Take Minutes
$numberOfRows = 50000; // Take Minutes
//$numberOfRows = 250000; // Takes Hours
for ($row = 1; $row <= $numberOfRows; $row++) {
    for ($column = 1; $column <= 26; $column++) {
        $columnChar = substr($columnLookup, ($column -1),  1);
        $spreadsheet->getActiveSheet()
                    ->getCell("{$columnChar}{$row}")
                    ->setValueExplicit(
                        "{$columnChar}{$row}",
                        \PhpOffice\PhpSpreadsheet\Cell\DataType::TYPE_STRING
                    );
    }
    if ($row % 1000 == 0) print "."; // show progress once in awhile..
}
print "\n";
print "[".date("Y-m-d H:i:s",time())."] End Data Population.\n";
print "[".date("Y-m-d H:i:s",time())."] Start File Creation.\n";
$writer = new Xlsx($spreadsheet);
$writer->setPreCalculateFormulas(false); // Has no affect given the spreadsheet has no formulas!
$writer->save('/tmp/xlsxExample.xlsx'); // This takes --forever--  ..but why?
print "[".date("Y-m-d H:i:s",time())."] End File Creation.\n";