phpdesktop-chrome - Not Working for Header in php

Question

I have a PHP file and whenever running a file in PHP phpdesktop-chrome (APP) I am getting below and I have only the following code in my file.

header("Content-Type: application/xls");
header("Content-Disposition: attachment; filename=filename.xls");
header("Pragma: no-cache");
header("Expires: 0");

Following is my error code.

Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\abc\www\backend\check.php:2)
Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\abc\www\backend\check.php:3)
Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\abc\www\backend\check.php:4)
Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\abc\www\backend\check.php:5)

Answer 1

Try to insert ob_start(); after the first <?php opening tag.