I think all answers are almost entirely correct, because SDK from the point of view can be almost anything, not that you just say "this is an SDK" for it to become something like this.
From what I've been observing the SDK does not necessarily need an IDE, or complete and ready tool, PHP is a server-oriented language and occasionally for CLI , that is, you can edit your documents in any editor and from what I understood with the examples quoted in both the question and the other answers is that SDK should be a complete kit to develop on the specific platform , then if it is possible with these repositories to "develop" your application (independent of anything extra) for PHP specifically, then yes, these repositories are SDKs.
Of course, in order to be able to fully develop, in the case of pagseguro-sdk , it seems that it contains a simulator of pagseguro next to the libraries, written in PHP itself ( link ).
Another thing I noticed in the facebook-sdk repository is that they have the docs folder ( link ), it contains the documentation, I do not see it as mandatory for an SDK, I believe that this should also define an SDK written in PHP, as it will make it independent of online sources.
It does not mean that they are really good SDKs, or that for these repositories the term SDK will fit well, but it is very likely that for something to be an SDK on the specified platform it will need something at least like < p>
- Full library or software
- Documentation (optional if you have external accessible fonts)
- This library has to work almost independently of anything (on the specified platform, in the PHP case)
So, in the PHP language the software that pagseguro-sdk and facebook-sdk depend on are only from their own libraries for development, and the additional things are your Software Development Kit (SDK), then an SDK can include anything as long as it serves as a "tool" for development on such a platform.
Points that would generate the counter of completion
Pagseguro does not have documentation together:
- I'd say it's a good library, but not a good SDK
Facebook depends on internet connection and use at least the sandbox (I believe):
Both rely on PHP to run the scripts:
- In the Android SDK you need Java to run, in the Microsoft SDK you need Windows to run, everything has some dependency, so I said "almost independent".