在PHP代码中集成PayPal

Question

I am finding my way out, integrating PayPal with PHP. But I have one question left. When reading this document: https://developer.paypal.com/docs/classic/ipn/gs_IPN/ PayPal recommends that we use:

header('HTTP/1.1 200 OK');

in order to to acknowledge receipt of the notification.

But in every tutorial I can find on the net, I see no trace of this.

Does that mean that it is after all not so important? Or otherwise where should one include this line?

Thanks for any tip.