Introduction
In the previous chapter, we covered how to handle error conditions by using PHP's built-in Exception class and how to use the try…catch block to control the flow of your application.
Most modern-day applications are built on top of an amalgamation of other open source libraries. Many problems that are frequently encountered across all applications have already been solved and tested by developers who have made their solutions freely available to include in your project. This may be as small as a library that generates unique identifiers, or as large as full application frameworks that help you to organize your code. Take authentication, for example. Nearly every PHP application is going to include some form of authentication and, the majority of the time, it will be built in exactly the same way each time. We make use of third-party solutions for authentication, so we don't have to write the same authentication code over and over again in each application...