If you want to send invoice file only when order in non-free – you need to do this:
- Create file /override/classes/order/Order.php with this contents:
1234567891011121314151617<?phpclass Order extends OrderCore{public function __construct($id = null, $id_lang = null){parent::__construct($id, $id_lang);if ($this->total_paid == 0) {$this->invoice_number = false;}}} - Remove file /cache/class_index.php
- Done!