Export data as CSV

CSV export in php

<?php 

$csv_data = generate_csv_file_data($from_date, $to_date);

header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private", false);
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"report.csv\";" );
header("Content-Transfer-Encoding: binary");

echo $csv_data;
exit;

/**
 * Example csv generation.
 */
function generate_csv_file_data(){
  $csv_output ='';

  $csv_header = array(
      'order_id',
      'order_key',
      'status',
      'order_user_name',
  );

  $i = 0;
  foreach($csv_header as $key => $head_name){
    $csv_output = $csv_output . $head_name . ",";
    $i++;
  }

  $csv_output .= "\n";

  $orders = [1,2,3,4,5,6,7];
  $csv_output .= $csv_output . $head_name . ",";

  for ($j = 0; $j < $i; $j++) {
    $csv_output .= $orders[$j] . 'test orderr'. ",";
  }

  $csv_output .= "\n";
	return $csv_output;
}


Reference Link
https://stackoverflow.com/questions/14160511/export-to-csv-wordpress/31038818