Regarding source folder hierarchy, there are always some common features, such as the
test folders, which have rather easy-to-understand contents.
However, I realized that big projects have both a
vendor folders, while I had always thought they were the same, as their names hint at including “third-party
libraries from external
vendors”. Though, seeing both in the same project means there is a difference.
Here is a more detailed example with Symfony: once you create a project, you get a
lib folder at the root of your project. In this folder, the following structure is found:
lib +--filter +--form +--… +--vendor +--simpletest +--symfony
symfony folder contains all Symfony's core.