So, visitor pays in PayPal website. After successful payment, PayPal redirects the visitor to `return` url ('return' => $some_url_i_defined,) and also PayPal sends confirmation to `notify_url` ('notify_url' => $other_url_i_defined,).
In `notify_url` file i process the response from PayPal. If all ok, record in mysql that order was paid.
And in `return` url i check my mysql data (check if the order was paid.
If visitor opens (is redirected) to `return` url before i executed code in `notify_url` file, then the visitor could not get what s(he) paid for.
So question is Can i be sure that paypal notify_url executes before return url ? I mean PayPal at first sends data to `notify_url` and only then redirects payer to `return` url?
What may be solution to be 100% sure that at first executes `notify_url `? To use some php `sleep`?