added compression for download and ensure utf-8 encoding

app/public/download_table.php

@@ -9,7 +9,8 @@
         $table = $_GET['table'];
     }
 
-    header('Content-type: text/csv');
+    ob_start('ob_gzhandler'); #compressing data which is sent to the browser, the browser will decompress the data automatically
+    header('Content-type: text/csv; charset="UTF-8" ');
     header('Content-Disposition: attachment; filename="table.csv" ');
 
 function download_table($stmt) {