In this example, two modules are created for different payment systems - PayPal and Stripe. Each of these modules implements the Module interface, which contains only one method, execute(). This method contains the specific functionality of each module, in this case, completing a payment via PayPal or Stripe. Package Library: In PHP, there are different package libraries that can be used to implement the Module model. One example is the Symfony framework, which has a modular architecture based on the Dependency Injection (DI) pattern, making it easy to add, remove or update functionality in a project. Another example is the Zend Framework, which also has a modular architecture, with each module exposing its own functionality, making it easy to reuse across web applications.