The quality of software, not only depends on its architecture and project management, but also is closely related with the code's quality. Bad, untidy code can run normally to some extent, but that will bring potential obstacles to the whole development team, as sure as a gun. As a result, that will greatly increase development time, resources and other costs. This same applies to both agile software development and traditional software development.

The classic PHP has won a rebirth, so it's time for the modern PHP to throw away its old burden and follow better practices. But almost all the existing PHP books and online tutorials have been out of date for a long time, such that it is difficult to reflect the new features and good practices of modern PHP.