Guzzle and cURL are http clients. When you use Guzzle or cURL for the first time you won’t know any difference, but many developers in GitHub prefer Guzzle over curl. Let’s see why they prefer Guzzle. Guzzle uses cURL by default, so many thinks that Guzzle requires cURL. Its not like that Guzzle can use any http client that you want other than cURL like PHP's stream wrapper, sockets, and non-blocking libraries like React. You can reuse code with Guzzle and its more simpler, cleaner, readable and reusable. It also allows you to do async requests in a  similar way we do with javascript using promises. It is easier to write unit tests for app and mock the http  requests with Guzzle.