HTTP extension that provides a convenient set of functionality Formula was removed
Last versions were

Revision: 2

php56-http requires the following formulae to be installed:
autoconf 2.69 Automatic configure script builder
libevent 2.1.8 Asynchronous event library
icu4c 61.1 C/C++ and Java libraries for Unicode and globalization

Recent formula history

ilovezfs php56: migrate to homebrew/core (#4835)
Sean Molenaar php-http: fix arguments to match dependencies
Sean Molenaar php-(intl|http) version bump
s172262 php56-http 2.6.0
Ben php56-http: rebuild bottle against libevent 2.1.8

Formula code at GitHub