WordPress Filters Reference

What a filter is. Before WP EasyCart uses a value, such as a list of columns, an email subject or a label, it passes the value through any filters you added. Your function can change it and hand it back. To react to an event instead, use an action.

Where to put your code. In a small plugin or your child theme’s functions.php. Never edit the WP EasyCart files; an update would remove your change.

A first example.
add_filter( 'wp_easycart_admin_subscriber_list_columns', 'my_columns' );
function my_columns( $columns ) { return $columns; }

Always return a value. A filter function must return the value it received, changed or not, or the setting it controls ends up empty. The first parameter in each entry is the value you receive and return; the rest are extra information. To receive extra values, add a count: add_filter( 'hook_name', 'my_function', 10, 2 );.