Among other features introduced in 2017.3 EAP we mentioned the editor-based REST client, which offers a new approach to working with web APIs.
Earlier, you could run your requests with the REST client built right into PhpStorm, but it required crafting each request by hand with lots of button clicking, adding and completing of fields, and so on.
What if we wanted to leverage the power of the PhpStorm editor for the very same task, with completions, refactorings, navigation, VCS capabilities and what not? That’s where the new editor-based REST client comes in. No more fiddling with tool windows: your HTTP requests are now first-class citizens in PhpStorm.