Code-Snippets-Functions/Execute a function on a child site/WooCommerce/add-attendees-emails-as-cc-for-woocommerce-processing-and-completed-email.txt

add_filter( 'woocommerce_email_headers', 'additional_cc_recipient', 10, 3 );
function additional_cc_recipient( $headers, $email_id, $order ) {
    // Only for Processing and Completed order email notifications
    if( in_array($email_id, ['customer_processing_order', 'customer_completed_order']) ) {
        if ( $count = $order->get_meta('cstm_items_count') ) {
            $recipient = []; // initializing

            for ( $i = 1; $i <= $count; $i++ ) {
                if ( $email = $order->get_meta('cstm_email'.$i) ) {
                    // Add attendees emails, avoiding duplicates
                    $recipient[$email] = utf8_decode($order->get_meta('cstm_full_name'.$i) . ' <' . $email . '>');
                }
            }
            $headers .= 'Cc: ' . implode(',', $recipient) . "\r\n";
        }
    } 
    return $headers;
}