I am developing a plugin where user will submit a form. The form submits to the same page. Form data handling code is implemented by checking the condition-
if ( !empty( $_POST['action'] ) && $_POST['action'] == 'customer_add_new')
Then the data is validated and entered to database using $wpdb->insert.
After that, I want to pass a variable to the URL, so that success message can be displayed and user can be stopped from re-submitting the form by refreshing the page. For that, I used-
$url = add_query_arg( array( 'customer_add_new' => 'success' ) ); wp_redirect( $url ); exit();
But this code is throwing the following error-
Warning: Cannot modify header information - headers already sent by (output started at E:\wamp\www\cp_plugin\wp-includes\class.wp-scripts.php:343) in E:\wamp\www\cp_plugin\wp-includes\pluggable.php on line 1216
I have successfully used the same code in the theme for this very same project. But the functionality was better suited for a plugin, than for a theme.