WWPP – Customize the admin “New Order” email subject for wholesalers

/**

 * Customize the Admin "New Order" email subject for wholesale customers only

 */

add_filter( 'woocommerce_email_subject_new_order', function( $subject, $order ) {

    if ( ! $order ) {

        return $subject;

    }

    $customer_id = $order->get_customer_id();

    if ( ! $customer_id ) {

        return $subject;

    }

    // List the wholesale roles you want to target

    $wholesale_roles = [ 'wholesale_customer', 'wholesale_vip' ];

    $user = get_userdata( $customer_id );

    if ( $user && array_intersect( $wholesale_roles, (array) $user->roles ) ) {

        // Matches the format: [{site_title}]: New Wholesale order #{order_number}

        return '[' . get_bloginfo( 'name' ) . ']: New Wholesale order #' . $order->get_order_number();

    }

    return $subject;

}, 10, 2 );