Getting Member Data From WhishList Member on Register

Please refer to the link below and read on how to use add_action correctly.
https://developer.wordpress.org/reference/functions/add_action/

add_action('wishlistmember_shoppingcart_register', 'get_member_info'));

function get_member_info() {
    // Debug $_POST.
    echo '<pre>';
    var_dump($_POST);
    exit;
}