Composer will solve the problem for you like this: a) You have a project that depends on library A. b) Among them, library A depends on other libraries, such as library B, library C, library D, library E, library F, library G, and library H. c) You only need to declare the library A you depend on. d) Composer will find out which version of the library A package needs to be installed, and install all the library packages that library A depends on (download them into your project).