commandcar is a CLI tool that can easily communicate with any API. It simplifies unreadable and complicated curl commands, and has some nice features to make automation of API calls much simpler and bash scripts more streamlined.
#curl
jakubroztocil/httpie
HTTPie is a command line HTTP client, a user-friendly cURL replacement. http://httpie.org
How to use curl_multi() without blocking
How to use curl_multi() without blocking
Good post on more efficient use of curl_multi() under PHP. Much better use of resources than most examples around the place.