enter code here
if(isset($_POST["export"]))
{    include 'database/config.php';
     include "database/database.php";
     $db = new database();
     $fn = "csv_".uniqid().".csv";

     $file = fopen($fn, "w");
     $query = "SELECT * from wp_terms";
     $read = $db -> select($query);
     fputcsv($file, array('ID', 'Name', 'slug', 'term group'));
     if($read) {
        while ($row = $read->fetch_assoc()) {
          fputcsv($file, $row);
        }
      }
     header('Content-Type: text/csv; charset=utf-8');
     header('Content-Disposition: attachment; filename="'.$fn);

     fclose($file);
   }