I have created a newsletter plugin. I have coded an export function, but I got this error:
Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\blog\wp-includes\script-loader.php:1005) in C:\xampp\htdocs\blog\wp-content\plugins\newsletter\export.php on line 4.
I tried many ways, but in vain. Please suggest me the best way to solve this issue.