Those who create commercial sites are faced with the question, "How should it receive payments?" One of the most popular payment systems in the world is PayPal. This system is often chosen because it is reliable, simple to use and allows an account to be easily opened. To open an account, you need only have a credit card and/or an account in an American bank. One of shortcomings of the system is its severe security policy. However, practice evinces that if you follow the rules of the system carefully, then errors are very rare. The purpose of this article is to show how payments processing can be organized to support reliability and security. The article is also aimed at providing you with an example of the development of a simple online shop, in order to demonstrate interaction with the PayPal system. You can use the code in your applications to organize interaction with the PayPal system and to process payments.