I want to call API using Phalcon Php framework. example: http://example.com?key=abc
Phalcon has no internally build way to ask other services.
You can use either client built in incubator project:
https://github.com/phalcon/incubator/tree/master/Library/Phalcon/Http/Client
or a standard connection class as Guzzle, or native php curl methods.