In this chapter, you have learned about the basic architectural principles of RESTful Web Services and also how to build one on your own using the Slim framework. We have also had a look at the PSR-7 standard that allows you to write HTTP components in PHP that are portable across frameworks and become highly re-usable. Finally, you have also learned how to use PHP's new MongoDB extension for both direct access to stored collections, and also in combination with other high-level abstractions, such as the GridFS standard.
Both your newly acquired Slim knowledge and your understanding of the PSR-7 standard will benefit you in the following chapter, in which you will build a real-time chat application using the Ratchet framework - and then use PSR-7 to integrate Ratchet with the Slim framework.