Dependency Management

You may be asking yourself why we need the complexity of another tool to manage our external dependencies for us. You could always just grab a copy of the source code and put it directly in your project. The answer is made apparent by one word in the question: external. The dependencies are not your code, and you don't want to be responsible for managing them. This becomes even more apparent as you consider that those packages are likely to also depend on other libraries, which may still have dependencies themselves, and so on. This is further complicated by the fact that each of these libraries needs to be compatible with each other over time as they implement new features, bug fixes, and security maintenance releases.

Composer does all the hard work of determining whether any of the libraries you depend on have upgrades available and determining which versions of those libraries are compatible with each other, and generates a verbose list of packages...